Cave Taxa Research Articles

Does the Cave Environment Reduce Functional Diversity?

Caves are not colonised by all taxa present in the surface species pool, due to absence of light and the tendency to food limitation when compared to surface communities. Under strong species sorting during colonisation and later by the restrictive environmental filter, traits that are not adaptive in subterranean habitats may be filtered out. We tested whether cave communities were assembled by the restrictive regime propitiated by permanent darkness or by competitive exclusion due to resource scarcity. When compared to surface communities, the restrictive subterranean regime would lead to lower functional diversity and phenotypic clustering inside the caves, and the opposite should be expected in the case of competitive exclusion. Using isopods (Oniscidea) as model taxa, we measured several niche descriptors of taxa from surface and cave habitats, used a multivariate measure of functional diversity, and compared their widths. We found phenotypic overdispersion and higher functional diversity in cave taxa when compared to surface taxa. On the one hand, the dry climate outside of caves hampered the survival of several taxa and their ecological strategies, not viable under severe desiccation risk, culminating in the clustering of functional traits. In contrast, this restriction does not occur inside of caves, where isopods find favourable conditions under lower predation pressures and more amenable environmental parameters that allow occupation and subsequent diversification. Our results showed that, at least for some taxa, caves may not be such a harsh environment as previously thought. The high functional diversity we found inside caves adds an additional reason for the conservation of these sensitive environments.

Islands within islands: Diversification of tailless whip spiders (Amblypygi, Phrynus) in Caribbean caves

Islands have played a key role in understanding species formation ever since Darwin’s work on the Galapagos and Wallace’s work in the Malay Archipelago. Like oceanic islands, habitat ‘islands’, such as mountaintops and caves similarly may drive diversification. Here we examine patterns of diversification in the tailless whip spider genus Phrynus Larmarck, 1809 (Amblypygida: Phrynidae) a system that shows evidence of diversification under the influence of ‘islands within islands’. We estimate phylogeographic history and measure genetic diversity among representatives of three nominal Phrynus species from epigean and cave systems of Puerto Rico and nearby islands. Data from five loci (mitochondrial 12S, 16S, Cox1; nuclear H3, 28S) were used to generate phylogenetic hypotheses and to assess species monophyly and phylogeographic relationships. Genetic divergences and population limits were estimated and assessed using the Geneious barcoding plugin and the genealogical sorting index. We find that mtDNA sequence divergences within each of the three Phrynus species range between 15% and 20%. Genetic divergence is structured at three spatial scales: among islands in a manner consistent with the GAARlandia hypothesis, among bedrock formations within Puerto Rico, and among caves within these formations. Every isolated cave system contains a unique mtDNA genetic lineage of Phrynus, with divergence among cave systems far exceeding that within. In some localities epigean specimens nest among cave taxa, in others caves are monophyletic. Remarkably, clades that show up to 20% mtDNA sequence divergence show little or no variation in the nuclear markers. We interpret this pattern as resulting from extreme conservation of our nuclear markers rather than male sex-biased dispersal, based on high conservation of 28S and H3 between our individuals and other amblypygid genera that are restricted to Africa. While this study includes but a tiny fraction of Caribbean caves, our findings suggest Phrynus may be much more diverse than hitherto thought, at least in terms of mtDNA diversity, and that the arthropod fauna of caves may represent a dimension of biodiversity that is yet to be discovered in the Caribbean biodiversity hotspot.

Danielopolina revised: Phylogenetic relationships of the extant genera of the family Thaumatocyprididae (Ostracoda: Myodocopa)

The extant genera of the ostracod family Thaumatocyprididae are revised using the results of a phylogenetic analysis based on 54 morphological characters and 28 taxa. This revealed two main lineages within the family. There is a deep-sea lineage comprising the two species of ThaumatocyprisMüller, 1906, the thirteen species of ThaumatoconchaKornicker and Sohn, 1976 and a monotypic DanielopolinaKornicker and Sohn, 1976, comprising the type species D. carolynaeKornicker and Sohn, 1976 only. The second lineage contained cave taxa only, all formerly placed in Danielopolina but here transferred to the subgenus Danielopolina (Humphreysella) Kornicker and Danielopol, in Kornicker et al., 2006, which is raised to full genus status as Humphreysella Kornicker and Danielopol, in Kornicker et al., 2006. This accommodates H. orghidani (Danielopol, 1972) new combination, H. bahamensis (Kornicker and Iliffe, 1989a) new combination, H. baltanasi (Kornicker in Humphreys et al., 2009) new combination, H. elizabethae (Kornicker and Iliffe, 1992) new combination, H. exuma (Kornicker and Iliffe, 1998) new combination, H. kakuki (Kornicker and Iliffe, 2000) new combination, H. mexicana (Kornicker and Iliffe, 1989a) new combination, H. palmeri (Kornicker et al., 2007) new combination, H. phalanx (Kornicker and Iliffe, 1995) new combination, H. styx (Kornicker and Iliffe, 1989c) new combination and H. wilkensi (Hartmann, 1985) new combination. The position of the remaining species, Danielopolina kornickeriDanielopol et al., 2000, in phylogenetic analyses is unstable, but this species is here recognised as a distinct lineage within the family. A new genus Welesina is established to accommodate as its type species Welesina kornickeri (Danielopol et al., 2000) new combination. New diagnoses are provided for all five genera. A new species of Thaumatoconcha, T. angeli sp. nov., is described, based on material of both sexes collected from deep water in the North Atlantic, on the Iberian abyssal plain. It can be readily distinguished from its congeners by the presence of 2 small bristles on the compound third-fourth antennulary segment of the female, and by the setation of the third endopodal segment of the antenna of the female.