Luís Carlos Crespo

Rapid biodiversity assessment of spiders (Araneae) using semi-quantitative sampling: a case study in a Mediterranean forest

Abstract.  1 A thorough inventory of a Mediterranean oak forest spider fauna carried out during 2 weeks is presented. It used a semi‐quantitative sampling protocol to collect comparable data in a rigorous, rapid and efficient way. Four hundred and eighty samples of one person‐hour of work each were collected, mostly inside a delimited 1‐ha plot. 2 Sampling yielded 10 808 adult spiders representing 204 species. The number of species present at the site was estimated using five different richness estimators (Chao1, Chao2, Jackknife1, Jackknife2 and Michaelis–Menten). The estimates ranged from 232 to 260. The most reliable estimates were provided by the Chao estimators and the least reliable was obtained with the Michaelis–Menten. However, the behavior of the Michaelis–Menten accumulation curves supports the use of this estimator as a stopping or reliability rule. 3 Nineteen per cent of the species were represented by a single specimen (singletons) and 12% by just two specimens (doubletons). The presence of locally rare species in this exhaustive inventory is discussed. 4 The effects of day, time of day, collector experience and sampling method on the number of adults, number of species and taxonomic composition of the samples are assessed. Sampling method is the single most important factor influencing the results and all methods generate unique species. Time of day is also important, in such way that each combination of method and time of day may be considered as a different method in itself. There are insignificant differences between the collectors in terms of species and number of adult spiders collected. Despite the high collecting effort, the species richness and abundance of spiders remained constant throughout the sampling period.

Species richness and composition assessment of spiders in a Mediterranean scrubland

Intensive fieldwork has been undertaken in Portugal in order to develop a standardized and optimized sampling protocol for Mediterranean spiders. The present study had the objectives of testing the use of semi-quantitative sampling for obtaining an exhaustive species richness assessment of spiders and testing the effects of day, time of day, collector and sampling method on the collected species richness and composition of a Mediterranean scrubland. The collecting summed 224 samples corresponding to one person-hour of effective fieldwork each. In total, 115 species were captured, of which 110 were recorded inside a delimited one-hectare plot, corresponding to more than 70% of the about 160 estimated species. Although no estimator reached the asymptote, the Michaelis-Menten curve behaviour indicates that the estimated richness should be accurate. Most different sampling approaches (day, time of day, collector and sampling method) were found to influence richness, abundance or composition of the samples to some extent, although sampling method had the strongest influence whereas “collector” showed no effect at all. The results support the idea that the only variables that need to be controlled in similar protocols are the sampling methods and the time of day when each method is executed. We conclude that populations in structurally simple habitats present narrower peaks of adult abundance, which implies higher percentages of juveniles in samples. Finally, results also indicate that habitats with a relatively simple structure like scrublands may require as much sampling effort, in order to reach similar proportions of captured species in relation to the estimated richness, as habitats that are much more complex.

Biogeographic patterns of spiders in coastal dunes along a gradient of mediterraneity

The Iberian Peninsula is recognized for its high levels of species richness, rarity and endemicity. Our main aim was to study biogeographic patterns of spiders in coastal dunes along a gradient of mediterraneity. Distance-decay of similarity, nestedness and co-occurrence metrics were used to explore spider’ distribution patterns. A similarity analysis was performed in order to obtain a hierarchical classification of sites. Indicator species analysis was conducted to identify indicator species for the various clustering levels of the site typology. The differentiation among assemblages was further explored by non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM). Assemblages’ similarity among sites decreased with climatic/geographic distance. The observed values of nestedness metrics (T and NODF) were not significant, while the co-occurrence metrics (C-score and Checkerboard units) were higher than expected by chance. Cluster analysis showed that spider’ assemblages were structured along a gradient from North to South, forming four geographically distinct clusters. ANOSIM tests and NMDS supported the biogeographic patterns identified by cluster analysis. Several indicator species were found for the different levels of the hierarchic site typology. Spider assemblages revealed a high degree of biogeographical structure along the Atlantic coast of the Iberian Peninsula. The coast is a “biogeographic crossroad”, encompassing faunistic elements of different origins. The hierarchic typology of sites is generally consistent with the major biogeographic regions and the thermoclimatic belts recognized for the region. Our results indicate that the climatic gradient and historic factors played a key role in the current spiders’ biogeographic patterns.

Determinants of spider species richness in coastal dunes along a gradient of mediterraneity

Abstract.  1. The Iberian Peninsula is one of the most relevant areas in terms of species richness, rarity and endemism in the Mediterranean Basin. Using spiders as a model, we studied the relative importance of environmental and non‐environmental spatial variation along a gradient of mediterraneity on the western coast of the Iberian Peninsula.

Optimal inventorying and monitoring of taxon, phylogenetic and functional diversity

1. Inventorying requires comprehensive sampling, while monitoring should build on it and focus on as few components as possible to detect changes in time or space. To sample or acquire information for both purposes can therefore be viewed as different processes, herewith called α-sampling and β-sampling. Biodiversity covers species, their genetic diversity and the way they interact in communities and ecosystems. Quantifying these aspects leads to the need to study taxon (TD), phylogenetic (PD) and functional diversity (FD). Here we propose and test a method for the optimization of sampling protocols to inventorying and monitoring TD, PD and FD for a wide range of taxa. 2. We used spiders as a case-study, although the same optimization procedure could be applied to any taxon requiring a combination of sampling methods. Spiders were sampled in multiple sites in the Iberian Peninsula. PD and FD were measured as the sum of the length of branches on a phylogenetic or functional tree. To reach the optimal combination of methods for inventory, we followed an iterative procedure optimizing the accumulation curve of diversity values. Optimal monitoring in space or time required minimizing the difference between sampled and true β-diversity. We used a framework that disentangles species replacement and richness differences contributions to overall β-diversity. 3. For α-diversity, the optimal combination of 24 samples for TD, PD and FD allowed sampling more than 50% of real diversity. For β-diversity, the optimal combination of six samples for all measures allowed reaching a bias (difference between sampled and true diversity) below 0.08. 4. The widespread use of similar sampling protocols worldwide and regular repetition in time can have a major impact on the scope and usefulness of global monitoring projects. In addition, the comparable sampling of biodiversity in space and/or time allows reusing of data collected for specific purposes, potentiating a synergistic effect among different projects. This makes data useful much beyond their initial plan. We strongly advocate the optimization, standardization and widespread adoption of sampling protocols for all taxa at a global level, for both inventory and monitoring of all levels of biodiversity: taxon, phylogenetic and functional.

Comparative phylogeography of endemic Azorean arthropods.

BackgroundFor a remote oceanic archipelago of up to 8 Myr age, the Azores have a comparatively low level of endemism. We present an analysis of phylogeographic patterns of endemic Azorean island arthropods aimed at testing patterns of diversification in relation to the ontogeny of the archipelago, in order to distinguish between alternative models of evolutionary dynamics on islands. We collected individuals of six species (representing Araneae, Hemiptera and Coleoptera) from 16 forest fragments from 7 islands. Using three mtDNA markers, we analysed the distribution of genetic diversity within and between islands, inferred the differentiation time-frames and investigated the inter-island migration routes and colonization patterns.ResultsEach species exhibited very low levels of mtDNA divergence, both within and between islands. The two oldest islands were not strongly involved in the diffusion of genetic diversity within the archipelago. The most haplotype-rich islands varied according to species but the younger, central islands contributed the most to haplotype diversity. Colonization events both in concordance with and in contradiction to an inter-island progression rule were inferred, while a non-intuitive pattern of colonization from western to eastern islands was also inferred.ConclusionsThe geological development of the Azores has followed a less tidy progression compared to classic hotspot archipelagos, and this is reflected in our findings. The study species appear to have been differentiating within the Azores for <2 Myr, a fraction of the apparent life span of the archipelago, which may indicate that extinction events linked to active volcanism have played an important role. Assuming that after each extinction event, colonization was initiated from a nearby island hosting derived haplotypes, the apparent age of species diversification in the archipelago would be moved closer to the present after each extinction–recolonization cycle. Exploiting these ideas, we propose a general model for future testing.

Species conservation profiles of endemic spiders (Araneae) from Madeira and Selvagens archipelagos, Portugal

Abstract Background The North Atlantic archipelagos of Madeira and Selvagens present a unique biological diversity including, presently, 56 endemic spider species. Several recent projects provide valuable information on their distribution across most islands and habitats. To date, the only endemic spider assessed according to the IUCN Red List criteria is Hogna ingens. The objective of this paper is to assess all remaining endemic species and advise on possible future conservation actions critical for the survival of endangered species. New information Seven species were found to have a continuing decline in either range or population size. Their decline can be mostly attributed to habitat destruction or degradation, invasive plant species that reduce quality of habitat, forest fires at high mountain regions and possible competition for resources from invasive congeners. The tetragnathid M. barreti is considered as possibly extinct due to the suspected impact of a competing species. Although most endemic spiders from the Madeira and Selvagens archipelagos have relatively low extinction risk due to the good condition and protection of the laurisilva forests where many live, there are a number of species requiring urgent attention and protection measures. These include all cave and mountain-restricted species as well as those threatened by competing congeners or invasive plants. Extending current protected areas, restoring original habitats of threatened species and the control of invasive taxa should remain a priority for species survival.

Species conservation profile of the cave spider Turinyphia cavernicola (Araneae, Linyphiidae) from Terceira Island, Azores, Portugal

Turinyphia cavernicola Wunderlich, 2008 is one of the two endemic cavernicolous spiders known from the Azorean archipelago (Portugal). In spite of relatively intensive searches, this species is known from only three caves, but with a single sustainable subpopulation restricted to the Algar do Carvão show cave. With an observed extent of occurrence (EOO) of 2 km2 and an area of occupancy (AOO) around 0,75 km2, it presents a restricted range, severe fragmentation, and continuing decline in EOO, AOO, habitat quality, number of locations and subpopulations caused by the ongoing threat from pasture intensification and tourist activities in the cave systems.

Spatial distribution of Madeira Island Laurisilva endemic spiders (Arachnida: Araneae).

Abstract Madeira island presents a unique spider diversity with a high number of endemic species, many of which are still poorly known. A recent biodiversity survey on the terrestrial arthropods of the native forest, Laurisilva, provided a large set of standardized samples from various patches throughout the island. Out of the fifty two species recorded, approximately 33.3% are Madeiran endemics, many of which had not been collected since their original description. Two new species to science are reported – Ceratinopsis n. sp. and Theridion n. sp. – and the first records of Poeciloneta variegata (Blackwall, 1841) and Tetragnatha intermedia Kulczynski, 1891 are reported for the first time for Madeira island. Considerations on species richness and abundance from different Laurisilva locations are presented, together with distribution maps for endemic species. These results contribute to a better understanding of spider diversity patterns and endemic species distribution in the native forest of Madeira island.

On the endemic spider species of the genus Savigniorrhipis Wunderlich, 1992 (Araneae: Linyphiidae) in the Azores (Portugal), with description of a new species

Savigniorrhipis topographicus new species is described from the Azores. The synapomorphies of Savigniorrhipis are discussed along with the affinities of the genus within the Savignia-group. Given the extremely restricted and increasingly disturbed habitat, S. topographicus new species should be classified as Critically Endangered and its single forest habitat at Topo (São Jorge Island) should increase its current protection level to a strict nature reserve.