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Three new hypogean species of the Iberian genus Roncocreagris Mahnert, 1974 are described from mainland Portugal: R. borgesi sp. nov. and R. gepesi sp. nov. from caves in the Sicó massif, and R. occidentalis sp. nov. from caves in the Montejunto and Cesaredas karst plateau. This brings to nine the number of known hypogean species of the mostly Iberian genus Roncocreagris: five from Portugal and four from Spain. Ecological comments and new localities for some of the previously known species are also included.
Using a comparative phylogeographic approach and different independent molecular clocks we propose a timescale for the evolution of troglobionts in the Dinaric Karst that is relatively consistent over a wide taxonomic range. Keystone events seem to belong to two age classes. (1) Major splits within holodinaric taxa are from the mid-Miocene. They present the potential upper limit for the age of cave invasions. (2) Regional differentiation, including speciation, which can at least in part be associated with a subterranean phase, took place from early Pliocene to mid-Pleistocene. We suggest two to five million years as the time when most of the analyzed lineages started invading the Dinaric Karst underground.
The evolution of troglobites comprises three distinct problems: cave colonization by an epigean ancestor, the evolution of troglomorphies, and intra-cave speciation. The study of cave-dwelling planthoppers has contributed much to our understanding of troglobite evolution and provides useful model systems to test various aspects of the theoretic framework developed in recent years. Most promising in this respect are taxa with several closely related but independently evolved troglobiontic lineages, such as on the Canary Islands, in Queensland/Australia and on the Hawaiian Archipelago. Closely related species often occur in caves with comparable ecological parameters yet differ in their age. Here we use comparative age estimates for Australian and Hawaiian cave cixiids to assess the dynamics of reductive evolutionary trends (evolution of troglomorphy) in these taxa and cave planthoppers in general. We show that the degree of troglomorphy is not correlated with the age of cave lineages. Morphological alteration may not be used to draw conclusions about the phylogenetic age of cave organisms, and hypotheses based on such assumptions should be tested in light of these findings.
An overview of the obligate hypogean fauna in Portugal (including Azores and Madeira archipelagos) is provided, with a list of obligated cave-dwelling species and subspecies, and a general perspective about its conservation. All the available literature on subterranean Biology of Portugal since the first written record in 1870 until today has been revised. A total of 43 troglobiont and 67 stygobiont species and subspecies from 12 orders have been described so far in these areas, included in the so-called Mediterranean hotspot of biodiversity. The subterranean fauna in Portugal has been considered moderately poor with some endemic relicts and it remains to be demonstrated if this fact is still true after investing in standard surveys in cave environments. The major problems related to the conservation of cave fauna are discussed, but it is clear that the protection of this specialized fauna implies an adequate management of surface habitats.
An overview of the obligate hypogean fauna in Portugal (including Azores and Madeira archipelagos) is provided, with a list of obligated cave-dwelling species and subspecies, and a general perspective about its conservation. All the available literature on subterranean Biology of Portugal since the first written record in 1870 until today has been revised. A total of 43 troglobiont and 67 stygobiont species and subspecies from 12 orders have been described so far in these areas, included in the so-called Mediterranean hotspot of biodiversity. The subterranean fauna in Portugal has been considered moderately poor with some endemic relicts and it remains to be demonstrated if this fact is still true after investing in standard surveys in cave environments. The major problems related to the conservation of cave fauna are discussed, but it is clear that the protection of this specialized fauna implies an adequate management of surface habitats.
Azorean lava-tubes and volcanic pits adequately sampled for arthropod fauna were evaluated for species diversity and rarity. An iterative partial multiple regression analysis was performed to produce a multi-criteria index (Importance Value for Cave Conservation, IV-CC) incorporating arthropod species diversity indices but also including indices qualifying cave geological and management features (e.g., the diversity of geological structures, threats, accessibility). Additionally, we calculated complementarity solutions (irreplaceability and Fraction-of-Spare measures) for each cave with different targets per species, i.e., the minimum number of caves needed for each species to be represented either once or twice. Our results clearly show that to preserve all troglobiont arthropods endemic to the Azores, it is crucial to protect several caves per island. As many as 10 and 15 caves are needed to include one or two occurrences, respectively, per species.
Cave-obligate organisms usually have smaller ranges and their assemblages have higher beta diversity than their epigean counterparts. Phylogenetic and functional diversity is usually low in cave communities, leading to taxonomic and functional disharmony, with entire groups missing from the subterranean realm. The objective of this work is to compare range, beta diversity, phylogenetic and functional diversity, taxonomic and functional disharmony of epigean versus troglobiont spiders in the Iberian Peninsula.
The median extent of occurrence was found to be 33 times higher for epigean than for cave species. Beta diversity was significantly higher for troglobiont assemblages. Cave assemblages present lower phylogenetic and functional diversities than expected by chance. Taxonomic disharmony was noticeable, with many speciose families, namely Gnaphosidae, Salticidae and Lycosidae, absent in caves. Functional disharmony was equally high, with ambush hunters and sensing web weavers being absent in caves.
The small range and high beta diversity of troglobiont spiders in the Iberian Peninsula is typical of many cave-obligate organisms, caused by the fragmentation and isolation of cave systems and the low vagility and high habitat specialization of species. Caves were colonized mainly by pre-adapted lineages, with high proportions of eutroglophile species. Some families no longer occur in surface habitats, possibly since the last glaciations, and currently are restricted to caves in the region. Few hunting strategies and web types are efficient in caves and these dominate among the troglobiont species.
As troglobiont communities are of low alpha diversity, with low functional redundancy, have narrow ranges, present high levels of population fragmentation and are taxonomically unique, they should present higher proportions of imperilled species than epigean spiders in the Iberian Peninsula. Some species are probably endangered and require urgent conservation measures.
Terrestrial animals in subterranean habitats are often classified according to their degree of morphological or ecological specialization to the subterranean environment. The commonly held view is that, as distance into a cave increases, the frequency of morphologically specialized, i.e., troglomorphic, species or ecological specialization will increase. We tested this hypothesis for the fauna in 54 caves in Slovenia–the classical land for subterranean biology. We found that there exist two ecologically well separated terrestrial subsurface faunas: one shallow and one deep. 1) The shallow subterranean fauna, adapted to the terrestrial shallow subterranean habitats (SSHs) in the upper 10 m of subsurface strata, is most diverse. It consists of randomly distributed non-troglobionts and a major group of troglobionts adapted to the soil root zone. 2) The deep subterranean fauna is represented by a minor group of troglobionts, adapted to caves. Troglobionts are strictly divided between the two faunas. There is strong evidence that in karstic ecosystems with deep-rooted vegetation this might be a global pattern, or that in these locations only the shallow subterranean fauna exist.
Terrestrial animals in subterranean habitats are often classified according to their degree of morphological or ecological specialization to the subterranean environment. The commonly held view is that, as distance into a cave increases, the frequency of morphologically specialized, i.e., troglomorphic, species or ecological specialization will increase. We tested this hypothesis for the fauna in 54 caves in Slovenia–the classical land for subterranean biology. We found that there exist two ecologically well separated terrestrial subsurface faunas: one shallow and one deep. 1) The shallow subterranean fauna, adapted to the terrestrial shallow subterranean habitats (SSHs) in the upper 10 m of subsurface strata, is most diverse. It consists of randomly distributed non-troglobionts and a major group of troglobionts adapted to the soil root zone. 2) The deep subterranean fauna is represented by a minor group of troglobionts, adapted to caves. Troglobionts are strictly divided between the two faunas. There is strong evidence that in karstic ecosystems with deep-rooted vegetation this might be a global pattern, or that in these locations only the shallow subterranean fauna exist.
Subsurface biota extends over a wide variety of habitats that can be spatially interconnected. The largest communities of this subsurface biota inhabit cavities and are well known mainly in caves where biologists are able to have access. Data about deep subterranean communities and arthropods living under one thousand meters was unknown. An expedition to world’s deepest cave, Krubera-Voronja in Western Caucasus, revealed an interesting subterranean community, living below 2000 meters and represented by more than 12 species of arthropods, including several new species for science. This deep cave biota is composed of troglobionts and also epigean species, that can penetrate until -2140 m. Deep subterranean ecosystems should not be seen only as an evolu- tionary dead end towards the troglomorphic syndrome, but also as a shelter for epigean species populations, especially during long periods of time when surface conditions are severe for their survival. Most of the subsurface biota depends on allochthonous sources of organic carbon coming from: water percolating from the surface, sinking streams that enter caves, and activities of animals mov- ing in and out of caves. The biocoenosis and the vertical distribution of invertebrate fauna of Krubera-Voronja are provided, from its entrance to the remarkable depth of 2140 meters, including the discovery of world’s deepest dwelling arthropod.
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