Scrublands and the sunlit side support highly diverse harvestmen (Arachnida: Opiliones) communities in two Iberian Mediterranean areas (Alicante, Spain)

Abstract

Dataset published through GBIF (DOI: 10.15470/obyxc1)

Key words: Sierra de Aitana, Parque Natural del Carrascal de la Font Roja, Iberian Peninsula, Community ecology, Spatial distribution, Phenology

Resumen

Datos publicados en GBIF (DOI: 10.15470/obyxc1)

Palabras clave: Sierra de Aitana, Parque Natural del Carrascal de la Font Roja, Península Ibérica, Ecología de comunidades, Distribución espacial, Fenología

Resum

Dades publicades a GBIF (DOI: 10.15470/obyxc1)

Paraules clau: Serra d'Aitana, Parc Natural del Carrascal de la Font Roja, Península Ibèrica, Ecologia de comunitats, Distribució espacial, Fenologia

Introduction

The coastal areas of Alicante province have experienced significant habitat fragmentation due to urban pressure. However, the interior mountainous regions have remained largely unchanged, preserving spaces of high ecological value. The Sierra de Aitana and the Carrascal de la Font Roja Natural Park are good examples, both characterised by a subhumid Mediterranean climate. The Sierra de Aitana is north-facing, resulting in lusher vegetation and greater humidity. Patches of holm oak Quercus ilex and pine Pinus halepensis can be found, accompanied by shrubs such as Pistacia terebinthus, Rosa pouzini, Lonicera implexa, and Rubus ulmifolius, among others (Diputación Provincial de Alicante 1984). In the Carrascal de la Font Roja Natural Park, there is a clear contrast between the sunlit and the shaded side due to its east-west mountain orientation. The south-facing, sunnier side has a drier and more arid climate, with isolated specimens of holm oak Quercus rotundifolia alongside shrubby and herbaceous vegetation. In contrast, the north-facing, shadier side falls within a wetter and more humid climatic unit, where a dense forest dominated by holm oak Q. rotundifolia and gall oak Quercus faginea prevails, with some pines P. halepensis interspersed (Riba et al 1980, Boronat et al 1989).

Harvestmen constitute the fourth most diverse order of arachnids, following Acariformes, Parasitiformes, and Araneae, with 6,855 described species (Kury et al 2024) found across all major continents except Antarctica. They are a common component of terrestrial ecosystems, where they interact with other taxa and play important roles in terrestrial ecological networks as both predators and prey (Pinto-da-Rocha et al 2007).

The structure and diversity of harvestmen communities are affected by multiple environmental factors, with microclimate, temperature, and humidity being among the most important (Todd 1949, Almeida-Neto et al 2006, Mitov 2007, Pinto-da-Rocha et al 2007). These factors, along with slope orientation –which influences temperature and humidity– and the physicochemical characteristics of the soil, are closely related to the type, structure, and composition of the vegetation (Proud et al 2011, Merino-Sainz and Anadón 2015, Colmenares et al 2016, Stašiov et al 2020, 2021).

They are a suitable subject for various ecological and biogeographical studies, primarily because they are sensitive to environmental conditions, susceptible to habitat alteration and fragmentation, and have a limited dispersal capacity, which requires the geographical continuity of favourable environments (Boyer et al 2007, Bragagnolo et al 2007, Mitov 2007, Pinto-da-Rocha et al 2007, Proud et al 2011, Stašiov et al 2021). However, research on the Iberian Peninsula has been predominantly faunistic and taxonomic. In recent years, several studies on the structure and ecology of Iberian harvestmen communities have been published, such as Merino-Sainz and Anadón (2015) for the Muniellos Biosphere Reserve (MBR) in Asturias, Merino-Sainz and Anadón (2018) for Monte Naranco in Oviedo (MNO), and Merino-Sainz et al (2020) for Monte Pedroso in Santiago de Compostela (MP). Additionally, two ecological reanalyses have been conducted founded on previous faunistic studies: Merino-Sainz and Prieto (2021), based on the data published by Rambla (1985) for the Macizo de San Juan de la Peña (MSJP) in Huesca, and Merino-Sainz and Prieto (2022), based on the data published by Rambla and Perera (1989) for Ordesa y Monte Perdido National Park (OMPNP) in the Huesca Pyrenees. Until now, research has primarily focused on the northern regions of the Iberian Peninsula, while other areas have not received the same attention. Therefore, this is the first study conducted in a Peninsular Mediterranean region.

So far, only two published studies involving annual sampling in the Iberian Peninsula –Rambla (1985) from Huesca (MSJP) and Merino-Sainz et al (2020) from Santiago de Compostela (MP)– have described the life cycles of Iberian harvestmen species.

This paper analyses the harvestmen community structure sampled in the Sierra de Aitana (SA) and the Font Roja Natural Park (FRNP) in Alicante, whose chorological information was previously published (Prieto et al 2024a). The objectives are: (1) to assess the reliability and quality of the inventory and calculate the expected gamma diversity at each sampling site; (2) to examine the observed richness (alpha diversity), abundance, species diversity, evenness, and dominance at each locality, along with the mean values for each vegetation group; (3) to analyse species distribution across different biotopes; (4) to characterise the spatial niches of the species and conduct an indicator species analysis for each vegetation type; and (5) to provide new ecological and phenological data on the collected species.

Material and methods

Study area

The study was carried out in the Sierra de Aitana (SA) and the Carrascal de la Font Roja Natural Park (CFRNP) in the province of Alicante (fig. 1A, 1B). The SA is a mountain massif located in the interior of the province of Alicante, within the municipality of Confrides, part of the Prebaetic Mountain range. It is the highest peak in Alicante (1,558 m a.s.l.) and one of the best examples of a high Mediterranean mountain ecosystem. It is particularly lush, retaining high humidity due to its north-facing orientation, in contrast to the drier southern slope. It has a subhumid Mediterranean climate, with an average annual rainfall of approximately 700 mm and a temperature range reaching 19ºC. Snowfall is relatively common in winter, especially at higher elevations (Diputación Provincial de Alicante 1984).

CFRNP is located in the outer areas of the Baetic Mountain Ranges, in the northwest of Alicante province, between the municipalities of Alcoi and Ibi. The highest point is the summit of the Sierra del Menejador (1,356 m a.s.l.). The Natural Park has a subhumid Mediterranean climate, with annual rainfall ranging from 750-850 mm and an average temperature of 4ºC in winter and 21ºC in summer. Owing to its altitude, snowfall and frost are frequent (Borreguero et al 1984). Due to its east-west orientation, there is a sunlit, south-facing side that is drier and more arid, and a shaded, north-facing side that is rainier and more humid (Riba et al 1980, Boronat et al 1989).

Study design and field data collection

Harvestmen from the SA were sampled by J. Hernández Corral between May 2021 and January 2022, primarily using pitfall traps, and occasionally through direct collection or entomological net sampling during trap collection dates. Two north-facing zones, A and B (fig. 1D), were sampled. In zone A, eight localities were sampled with 12 pitfall traps (fig. 2C, 2D, 2F), and in zone B, one locality with a single pitfall trap was sampled (fig. 2D, table 1). The pitfall traps were covered with stones and filled with a 50 % propylene glycol solution, with a small amount of detergent to reduce surface tension.

Harvestmen from CFRNP were sampled using pitfall traps by Juan P. García-Teba over a ten-month period between 2020 and 2021, during a sampling to study coprophagous beetles. The pitfall traps, 20 cm in diameter and spaced 20 m apart, were collected twice a month whenever possible (table I in Barrientos et al 2023). Four localities were sampled, each with two pitfall traps (fig. 1C, table 1). FP1 and FP2 were north-facing (shaded side, fig. 2A), FP3 was located on the summit with a sunlit orientation, and FP4 was south-facing (sunlit side) (fig. 2B). The pitfall traps were covered with mesh, with cow dung placed in the central part as bait, and filled with a 50 % propylene glycol solution (Barrientos et al 2023). Collected specimens were preserved in 70 % ethanol, with labels indicating their location, altitude, date, sampling method, habitat, and collector. The samples are housed in the private collection of J. Hernández-Corral.

Statistical analyses

For the statistical analysis, individuals sampled using pitfall traps in the SA were included, along with ten specimens of Odiellus levantinus– eight captured by hand and two through vegetation sweeping with an entomological net. These specimens were collected on the same dates and within the sampled localities (BP11 and AP7) as the pitfall trap specimens. Nevertheless, eight individuals caught by hand from different localities than those sampled were excluded from the statistical analysis. Additionally, in CFRNP, one O. levantinus specimen trapped using a pitfall trap but lacking a label was also excluded. These individuals did not provide any novel data, as they belonged to the most abundant and frequently recorded species. However, they were included in the phenological study.

The localities were grouped based on vegetation structure in the two study areas. In the SA, three groups were established: Group 1 included two pine forest localities (BP11 and AP2); Group 2 comprised three scrubland localities (AP1, AP5, and AP6); and Group 3 consisted of three abandoned terraces invaded by herbaceous species (AP3, AP4, and AP7). In CFRNP, two groups were defined: Group 1 included two localities with pine and holm oak forests on the shaded side (FP1 and FP2), while Group 2 comprised two localities with holm oak forests on the sunlit side (FP3 and FP4) (table 1).

To address the first objective, accumulation curves, a parametric estimator, and four non-parametric estimators were used to assess the reliability and quality of the inventory, as well as to estimate the expected total species richness (gamma diversity). The smoothed accumulation curve for the dataset was obtained using sampling dates as the unit of sampling effort and randomized 999 times in PRIMER® (Clarke and Gorley 2006). The Clench function was fitted to the smoothed curves to estimate the asymptote using the Simplex and Quasi-Newton methods (Jiménez-Valverde and Hortal 2003) in STATISTICA® (StatSoft 2011). Three non-parametric estimators based on incidence (Chao2, Jackknife 1, and Jackknife 2) and one based on abundance (Chao1) were applied, all implemented in PRIMER®. To achieve the second objective, the observed species richness (alpha diversity) and abundance at both locality and group levels were analysed. In addition, the diversity of the community was characterized using Hill numbers of order q = 0 to q = 3, where ⁰D represents species richness, ¹D corresponds to Shannon diversity (exp H'), ²D is the inverse of Simpson's index (1/D), and ³D is the inverse of the Berger-Parker index (1/d) (Hill 1973). Calculations were performed in R (v. 4.0.3) (R Development Core Team 2014) using custom functions and the "ggplot2" package to visualize diversity profiles. To accomplish the third objective, an analysis of similarity (ANOSIM) was conducted to test the null hypothesis of the absence of significant differences in harvestmen assemblages between localities, using abundance data and the Sørensen similarity index in PRIMER®. The percentage of dissimilarity between localities, the internal similarity within each locality group, the dissimilarity between groups, and the contribution of each species to that dissimilarity were determined using similarity percentage analysis (SIMPER), based on abundance data and using the Bray-Curtis similarity index in PRIMER®. Additionally, a non-metric multidimensional scaling analysis (NMDS) was performed using Bray-Curtis as the dissimilarity measure, implemented in the "vegan" package in R. For the fourth objective, the species spatial niche breadth was estimated using the Hill index (N²) in PRIMER® and Indicator Species analyses were conducted with the "indicspecies" package in R (De Cáceres et al 2012). For the final objective, the phenology of species with more than 19 specimens was studied. Phenological graphs were created in EXCEL®, representing a full year from January to December and displaying the abundance of males, females, and immatures per month. For the phenological study, all individuals were included, even those excluded from the statistical analysis. The graphs also distinguished between the absence of specimens (value = 0) and months that were not sampled.

Results

Alpha and Gamma diversities

A total of 847 harvestmen belonging to 10 species were collected. Nine individuals were excluded from the statistical analyses, leaving 838 for inclusion: 479 from CFRNP (185 males, 172 females, and 122 immatures) and 359 from the SA (104 males, 82 females, and 173 immatures) (table 2A, 2B). See also dataset published through GBIF, DOI: 10.15470/obyxc1).

The Clench function showed a good fit to the smoothed accumulation curves of the dataset for both the SA and CFRNP, with determination coefficients close to 1 (R² ≥ 0.98). The inventories were sufficiently reliable and complete, as the slopes of the curves fitted to the Clench function (p) were less than 0.1, the values of the inventoried proportion (q) exceeded 0.7, and the percentages of variance explained were above 98 % (Jiménez-Valverde and Hortal 2003). The total observed species richness in each area (gamma diversity) closely approximated both the number of species predicted by the asymptote of the Clench function (S_esp) and the estimates provided by non-parametric estimators. The highest estimates were obtained from the Jackknife estimators, which predicted two additional species for the SA and one for CFRNP (table 3).

In CFRNP, 479 individuals belonging to eight species (gamma diversity) were studied, with an average diversity of 5.5 species per locality. The sunlit localities (Group 2: FP3 and FP4) exhibited a maximum diversity of seven species, while the shaded ones (Group 1, FP1, and FP2) had a minimum of four species. The sunlit sites exhibit higher alpha diversity across all orders of q, indicating a greater number of species and lower dominance, although FP3 has a flatter profile, indicating lower evenness (tables 2A, 4A, fig. 3A). In the SA, 359 harvestmen belonging to nine species (gamma diversity) were studied, with an average diversity of 3.4 species per locality. The highest diversity was recorded at a scrubland locality (AP1, Group 2) with seven species, while the lowest was observed in a grassland (AP4, Group 3) with just one species. Shrublands in Group 2 (AP1, AP5, and AP6) harbor richer and more balanced communities compared to pine forests and grasslands, which have poorer communities dominated by a few species, especially in the case of grasslands (tables 2B, 4B, fig. 3B).

Harvestmen communities in different biotypes

For CFRNP, an NMDS analysis was deemed unnecessary, as it would not provide relevant results due to the low number of sampled localities.

The ANOSIM similarity analysis revealed significant differences between groups (table 5A). However, the SIMPER analysis indicated a 53 % dissimilarity between the two groups, with Homalenotus coriaceus contributing the most to this dissimilarity (table 6A). The localities in Group 1 (shaded side) presented a similar faunal composition, as the ANOSIM did not find statistically significant differences among them (n.s. = p > 0.05) (table 5A). In contrast, the localities in Group 2 (sunlit side) showed significant differences according to the ANOSIM test (table 5A). However, the SIMPER reported only a 29 % dissimilarity among them (table 5A) and an average internal similarity of 71 % (table 6A). In the holm oak Q. rotundifolia, gall oak Q. faginea, and pine P. halepensis localities of Group 1 (FP1 and FP2), 93 specimens from five species were recorded (average richness: 4). Meanwhile, in the holm oak Q. rotundifolia and shrubby and herbaceous vegetation localities of Group 2 (FP3 and FP4), 386 individuals from seven species were collected (average richness: 7) (table 2A). The localities shared four frequent and abundant species: Phalangium minus, Odiellus levantinus, Nelima hispana, and Cosmobunus granarius. Odiellus ramblae was found only in a shaded locality (FP1), while three species were exclusive to the sunlit zone: Trogulus schoenhoferi, Calathocratus zaragozai, and the most abundant H. coriaceus. Almost all species were more abundant in the sunlit localities, except for O. ramblae, which only occurred in FP1, and P. minus, which was evenly distributed across all four localities.

For the SA, the NMDS analysis indicated a stress value of 0.1. Along the first ordination axis, on the positive side, there were two grassland localities from Group 3 (AP3 and AP4) and the only pine forest sampled in Zone B (BP11, Group 1). The remaining localities were placed on the negative side, with a pine forest in Zone A (AP2, Group 1) positioned farther from the others (fig. 4). The ANOSIM similarity analysis suggested that the localities in the SA had a similar faunal composition (n.s. = p > 0.05), except for AP2 (Group 1), which displayed statistically significant differences (p ≤ 0.05, p ≤ 0.01) from the pine forest of the same group (BP11) and from three other localities (AP1, AP6, and AP7) (table 5B). The SIMPER analysis revealed that AP4 –with only one species (tables 2B, 4B)– and AP2 –with low diversity, low evenness, and high dominance (tables 4B, fig. 3B), had the highest dissimilarity percentages (table 5B). Furthermore, the same test showed that Group 2 (scrubland) had the highest average internal similarity percentage, followed by Group 3 (grassland) and Group 1 (pine forests) (table 6B), as also reflected in the NMDS (fig. 4). The dissimilarity percentages between the groups were approximately 50 %, with P. minus and O. levantinus being the main contributors to this dissimilarity (table 6B). In the pine forest localities of Group 1 (AP2 and BP11), 44 specimens from five species (mean richness: 3) were collected. In the scrubland localities of Group 2 (AP1, AP5, and AP6), 199 harvestmen from eight species (mean richness: 5.3) were recorded. In the herbaceous localities of Group 3 (AP3, AP4, and AP7), 116 individuals from six species (mean richness: 3) were captured (table 2B). The groups shared the four most frequent and abundant species, along with Phalangium opilio. Scrublands had three unique species (O. ramblae, T. schoenhoferi, and Dicranolasma soerensenii), while C. zaragozai was only found in a grassland (AP7). Almost all species were located on the negative side, next to the most diverse localities (AP1, AP5, AP6, and AP7), except for O. levantinus and P. opilio, which were placed on the positive side.

Spatial niche width

In CFRNP, O. levantinus, P. minus, and N. hispana, present at all four localities, and C. granarius, despite having only 19 individuals across three localities, had a broad niche (N₂ > 2.3). The remaining species displayed a narrower niche (N₂ < 4), including H. coriaceus, which, although the most abundant in this area, showed high dominance in FP3 (94.9 % of the specimens) (table 2A).

In the SA, O. levantinus, P. minus, N. hispana, and C. granarius again exhibited the broadest spatial niche widths (N₂ > 3), despite variations in specimen counts, with C. granarius and N. hispana having 22 and 23 individuals, respectively (table 2B).

Indicator species

In the SA, two indicator species were identified for Group 2 (scrubland): C. granarius and P. minus, both with an indicator value of 0.9 (p ≤ 0.05).

Phenology

The species studied (those with more than 19 recorded specimens) were O. levantinus, N. hispana, P. minus, and C. granarius in both samplings, and H. coriaceus in CFRNP (fig. 5). These records represented the first phenological data for the recently described O. levantinus and the first obtained from a systematic annual sampling for N. hispana and H. coriaceus. Certain biases must be considered when drawing solid conclusions about the species' life cycle. The sampling showed some temporal irregularities, as April was the only month not sampled, and losses occurred due to evaporation in the summer months and destruction by wild boars. When comparing the graphs of both areas, the presence of adults coincided, but differences were observed in the occurrence of immatures. All species displayed stenochronous development, with adults present for only a few months. Two species (C. granarius and H. coriaceus) registered adults primarily in late summer-autumn, two others (O. levantinus and N. hispana) had an autumn-winter phenology, and P. minus matures in winter-spring.

Discussion

Richness and distribution of harvestmen species

A harvestmen community comprising eight species in CFRNP and another with nine species in the SA has been studied (tables 2A, 2B), with seven species in common. Three additional species must be added to the SA (Odiellus bicochlearius, Anelasmocephalus ortunioi, and Leiobunum levantinum), and two more to CFRNP (D. soerensenii and L. levantinum) (table 7), when considering the results from an additional three-month sampling of the colluvial Mesovoid Shallow Substratum (MSS, see description in Ortuño et al 2013), carried out in both areas between 2011 and 2013 (Jiménez-Valverde et al 2015, Prieto and Las Heras 2020, Prieto et al 2024a, 2024b, Gilgado et al in prep.). This implies that CFRNP hosts a harvestmen community of 10 species and the SA one of 12 species –one more than the highest estimate offered by the estimators in both samplings (table 3). This highlights the relevance of the MSS as a refuge for endemic and rare species, revealing significant faunistic information, providing new taxa, reporting notable records of poorly known species, and supporting the completion of fauna inventories (Jiménez-Valverde et al 2015). With the inclusion of MSS sampling, the two study areas share nine species, with H. coriaceus present only in CFRNP, and A. ortunioi, P. opilio, and O. bicochlearius found exclusively in the SA.

According to Pinto-da-Rocha et al (2007), the species richness of European harvestmen communities in a single locality can range from two to 19 species. The highest recorded local species richness in the Iberian Peninsula was 19, observed in the MBR in Asturias (Merino-Sainz and Anadón 2015).

Among the species recorded in this study, only P. opilio has a Palaearctic distribution and is the only one present in all other studies from the Iberian Peninsula. The remaining species has a Mediterranean distribution. H. coriaceus and D. soerensenii have a western Mediterranean range, while C. granarius has a Betic-Riffean distribution. The other six species are Iberian endemics: P. minus and O. ramblae from Cataluña and Comunidad Valenciana; N. hispana and C. zaragozai from Valencia and Alicante provinces; and O. levantinus and T. schoenhoferi from Alicante province (Prieto et al 2024b).

Harvestmen communities across different biotypes

The results indicate that harvestmen communities vary according to distinct plant assemblages, supporting previous studies suggesting that their structure is influenced by multiple environmental factors closely related to vegetation type, structure, and composition (Almeida-Neto et al 2006, Mitov 2007, Proud et al 2011, Merino-Sainz and Anadón 2015, Colmenares et al 2016, Stašiov et al 2020, 2021).

Pinto-da-Rocha et al (2007) suggest that forest habitats offer greater structural complexity, providing more resources, higher microclimatic stability, and a greater diversity of microhabitats, all of which positively affect harvestmen communities. In contrast, open habitats are more exposed and experience pronounced seasonal fluctuations in abiotic factors, primarily temperature and humidity. These conditions limit the presence of many harvestmen species while favouring the dominance of one or a few species. In the Iberian Peninsula, this premise is supported by findings from the MBR, the MSJP, and OMPNP, where forested areas hosted greater harvestmen abundance and richness, exhibited higher diversity, and displayed lower dominance than open environments (Merino-Sainz and Anadón 2015, Merino-Sainz and Prieto 2021, 2022). However, the wooded areas of the low-altitude Cantabrian territories were not as rich as expected, with scrubland and boundaries being the most diverse. Moreover, grasslands supported a unique and exclusive harvestmen assemblage, along with an unexpectedly high abundance of two Homalenotus species (Merino-Sainz and Anadón 2018).

Species aggregates characterising each locality can reveal differences between localities with the same vegetation type, reflecting specific abiotic factors that influence the microclimate (Mitov 2007, Merino-Sainz and Anadón 2015). In the MBR, two main forest clusters were identified, distinguishing forests with richer soils, located in the lower valley, from those at higher elevations (Merino-Sainz and Anadón 2015). In the MSJP, an open holm oak woodland ("carrascal", Q. rotundifolia) was the locality with the highest "true" diversity (²D) value (Merino-Sainz and Prieto 2021). As suggested by Rambla (1985), this could indicate a microclimate that serves as a refuge for these species, such as the environment beneath the holm oak canopy, where leaf litter accumulates and a diverse shrub border of Mediterranean species develops.

In CFRNP, localities of the sunlit side (Group 2), with less tree cover and more sunshine, exhibited greater diversity, species richness, and abundance of harvestmen, in contrast to localities on the shaded side (Group 1), which had higher humidity and tree cover (table 4A). According to the SIMPER test, Group 2 had the highest internal similarity (71 %) (table 6A), although the ANOSIM test detected significant differences (p ≤ 0.01) between localities (table 5A). These differences may be attributed to the uneven distribution of H. coriaceus and O. levantinus, as they were significantly more abundant in FP3, located at the summit, on the south-facing side, but between the two slopes. According to Hill numbers and diversity profiles based on Hill numbers, FP4 and FP3 show the same species richness (⁰D). However, FP4 exhibits the highest diversity across all orders q (^qD), indicating not only high richness but also a relatively even distribution of abundances. In contrast, FP3 shows lower evenness (¹D) and a marked dominance by a few species (²D, ³D) (table 4A, fig. 3A).

In the SA, scrublands (Group 2) showed the highest internal similarity in terms of species composition (70.5 %), according to the SIMPER test (table 6B) and NMDS (fig. 4). This group includes the three most diverse localities, with the highest evenness and lowest dominance (AP1, AP5, and AP6) (table 4B), as well as three exclusive species (T. schoenhoferi, O. ramblae, and D. soerensenii) (table 2B). Similarly, scrublands and boundaries exhibited the highest species richness, diversity, and abundance of harvestmen in MN (Merino-Sainz and Anadón 2018).

As reported by the ANOSIM, SIMPER test, and NMDS analysis, AP2 (Group 1) was the most distinct locality (table 5B, fig. 4), being the only one without the most abundant species, O. levantinus (table 2B). Pine forests (Group 1) exhibited the lowest internal similarity (table 6B), with differences observed between localities (AP2 and BP11) (table 5B). BP11, a repopulated pine forest located far from the other localities in zone B, lacked a shrub border and had bare soil covered by a layer of pine needles. It was poor in species, with low diversity and high dominance of O. levantinus (tables 2B, 4B). In theory, this locality could be a suitable habitat for harvestmen, particularly immatures, which find moisture in the soil beneath the pine needles. However, the absence of shrub cover, which also serves as a refuge for immatures (Rambla 1966, 1985), may explain the low diversity observed. Finally, Group 3 comprises two contiguous, exclusively herbaceous localities (AP3 and AP4) –characterized by very low diversity, low evenness, high dominance by O. levantinus, and markedly shallow profiles (tables 2B, 4B, fig. 3B)– and another locality (AP7) with higher species richness, abundance, and diversity (table 4B), situated near scrublands in the NMDS (fig. 4). AP7 received a higher sampling effort, with six pitfall traps, due to its greater variety of microhabitats, which was reflected in its high species richness and specimens abundance (table 2B). Herbaceous formations typically support low species richness and diversity in harvestmen but sustain high abundance of a few dominant species (Merino-Sainz and Anadón 2018, Merino-Sainz and Prieto 2021, 2022).

Ecology of harvestmen species

The most abundant and ecologically versatile species, those with the greatest niche breadth and presence across all habitat types, were O. levantinus, P. minus, N. hispana, and C. granarius. H. coriaceus was the most abundant species, but it was only found in CFRNP. However, it had a narrow niche, as it occurred only on the sunlit side, predominantly in FP3. Other species of the genus (H. quadridentatus and H. laranderas) exhibited similar behavior in the low-altitude Cantabrian territories, as they were extraordinarily abundant, but predominantly found in meadows, where they were dominant, had a narrow niche, and acted as indicator species of the same, contributing the most to the identity of the cluster (Merino-Sainz and Anadón 2018).

The remaining species were scarce, infrequent, and had a narrow niche breadth. However, all were recorded in the MSS sampling, except for P. opilio. Notably, species that were rare in the pitfall sampling (such as O. ramblae, T. schoenhoferi, C. zaragozai, and D. soerensenii), were present in the MSS, with some, like D. soerensenii, being exceptionally abundant (table 7). Given that MSS sampling lasted only three months, this further highlights its importance (Jiménez-Valverde etal 2015, Prieto and Las Heras 2020, Prieto et al 2024a, 2024b, Gilgado et al in prep.).

C. granarius is a frequent and widespread species in the Iberian Mediterranean coastal regions (south and east peninsular). It inhabits damp and shaded environments, such as the walls of dwellings, tunnels, caves, and under bridges. It usually forms aggregations of numerous individuals in compact masses (Rambla 1970). In the SA, it was an indicator species for scrublands (Group 2), while in CFRNP, it was more abundant on the sunlit side, which does not coincide with Rambla’s descriptions (1970).

N. hispana is an Iberian endemic species known only from the provinces of Valencia and Alicante. In this study with pitfall traps, it was an abundant species, especially in scrublands, but it was also an abundant species in the MSS (table 7) (Prieto et al 2024b).

In general, other Iberian Odiellus species (such as O. troguloides, O. seoanei, and O. simplicipes) and P. opilio were abundant and frequent, with high niche breadth values, except for P. opilio in MP and O. seoanei in MN. These species preferred more xerophilus and exposed habitats, forming an aggregate of the driest localities. P. opilio was an indicator species for these environments (Merino-Sainz and Anadón 2015, 2018, Merino-Sainz et al 2020, Merino-Sainz and Prieto 2021, 2022). P. minus was described from open Mediterranean pine P. halepensis and holm oak Q. ilex forests with heather Erica multiflora cover in Barcelona province (Rambla 1966, as Dentizacheus minor). Immatures were predominantly found in soil with a high accumulation of pine bark and leaf litter, while adults occupied the shrub layer and the lower branches of trees (Rambla 1966). O. ramblae inhabited pine forests P. halepensis with some holm oaks Q. ilex and Chamaerops humilis, at its type locality in the southern region of Cataluña (Sánchez-Cuenca and Prieto 2014).

In this study, there was a significant difference in abundance between Odiellus and Phalangium, with one genus being considerably more abundant than the other. O. levantinus and P. minus were both abundant and frequent species, showing the highest niche breadth values, whereas O. ramblae and P. opilio were rare. This pattern has also been observed in other studies where two different Odiellus species cohabit: O. simplicipes dominatesover O. seoanei in the RNIM and MN (Merino-Sainz and Anadón 2015, 2018) and O. troguloides dominates over O. simplicipes in OMPNP (Merino-Sainz and Prieto 2022).

Despite being a scarce species with a narrow niche, P. opilio was found in all three vegetation groups. O. ramblae was only recorded in scrubland in the SA and in a shaded locality in CFRNP. P. minus was an indicator species for scrubland in the SA, while in CFRNP, it was uniformly distributed across the four localities. Finally, O. levantinus was present in all vegetation groups, being more abundant on the sunlit side in CFRNP, as well as in grasslands and scrubland in the SA.

Regarding the species with low frequency and/or narrow niches, it is possible that they have specialized ecological requirements or particular adaptations to specific microhabitats, or that the sampling method used was not the most suitable for detecting them. As previously mentioned, other species of the genus Homalenotus predominantly occupy grasslands (Merino-Sainz and Anadón 2018). The trogulids (T. schoenhoferi and C. zaragozai), and D. soerenseniiwere much more abundant when sampling the MSS, although in other studies using pitfall traps, trogulids were also quite abundant (Merino-Sainz and Anadón 2015, 2018, Merino-Sainz et al 2020, Merino-Sainz and Prieto 2021). P. opilio was much more abundant when shrubs or tree branches were sampled using active methods such as vegetation beating or entomological net sampling (Merino-Sainz and Anadón 2015, 2018). Finally, among the Odiellus species, which appear to share the same ecological requirements and occupy the same habitat, some form of competition may occur, the causes of which remain unknown and would be of interest for future studies.

Phenology

Belozerov (2012) states that most harvestmen species in temperate regions are stenochronous, a finding supported by our results (fig. 5). In agreement with the observations of Rambla (1970) regarding individuals kept in captivity in the epigean environment, C. granarius is a species with adults present in early summer. They lay eggs and die in autumn, and the eggs spend the winter buried in the soil, hatching at the beginning of spring. Nymphs are abundant in April and May. Our results align with Rambla`s observations (1970), as we found similar patterns when comparing data from the two areas.

Furthermore, Rambla (1966) observed that P. minus appears in spring, lays eggs at the end of May, and hatches in October and November. This observation is corroborated here, as adults appeared from January to June, with a peak in spring (April was not sampled), and they hatched in autumn-winter.

H. coriaceus exhibited an annual cycle, with adults present from August to March, peaking in abundance in August, and immatures from November to March. In other localities from Alicante within the MSS (Prieto et al 2024b), adults were found from September to January. According to several authors, species of the genus Homalenotus have long-lived adults that lay multiple clutches throughout the year, such as H. quadridentatus, which is considered a species with eurychronous development (Juberthie 1964, Sankey and Savory 1974, Martens 1978, Rambla 1985). However, the two Homalenotus species collected in Monte Pedroso, H. quadridentatus and H. laranderas, were stenochronous (Merino-Sainz et al 2020), as was H. coriaceus in the present study.

Adults of N. hispana were present from October to January. Immatures appeared in October, overlapping with adults, and persisted until May in SA (April was not sampled). Recent data from the MSS in SA and other localities in Alicante (Prieto et al 2024b) recorded both adults and immatures in January and October, which aligns with our findings. European species of this genus exhibit an annual cycle, maturing in late summer, mating and laying eggs in autumn, hatching in late winter, and growing during the spring and summer months (Martens 1978, Wijnhoven 2009 ). N. doriae in Holland likely has two generations per year (Wijnhoven 2009), which may explain the presence of immatures of N. hispana in October.

O. levantinus had adults primarily in autumn and winter, although some individuals may survive until March. Immatures were present from May to December, with the highest abundance in August. Other Odiellus species studied in the Iberian Peninsula also display stenochronous development, with adults appearing in autumn and winter. O. troguloides in the MSJP of Huesca presented adults from July to January, peaking in October, and immatures from March to August, with a peak in June and July (Rambla 1985). O. seoanei in MP of Santiago de Compostela had adults from July to January, peaking from September to November, and immatures from April to September (Merino-Sainz et al 2020).

Perspectives for future conservation strategies

Although both study areas are protected for the conservation of their biodiversity, landscape, and cultural heritage, this study and other recent ones (Barrientos and Hernández-Corral 2022, Barrientos et al 2023) highlight their high ecological value, revealing new species and providing new data on others that significantly expand their known distribution ranges (Prieto et al 2024b). Therefore, these new data can contribute to improve natural resource management and the development of conservation strategies in Mediterranean ecosystems. In this case, the results underscore the importance of focusing efforts on specific habitats, such as Mediterranean shrublands dominated by Q. Rotundifolia, which can create a microclimate suitable for the development of certain harvestmen species, as observed by Rambla (1985).

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