Diversidade funcional e negra de isópodes subterrâneos em áreas cársticas do centro-leste do Brasil
Abstract
We addressed the mechanisms responsible for the composition of subterranean
communities and its consequences for the maintenance of ecological processes. In the first
chapter, we tested whether cave communities were assembled by the restrictive regime
propitiated by permanent darkness, or by limiting similarity caused by competitive exclusion
when compared to surface communities. With this purpose, we measured several niche
descriptors of species from inside and outside caves using a multivariate measure of
functional diversity and compared their widths. Our results showed that isopods found
inside caves favourable conditions to allow occupation and diversification, with milder
environmental parameters coupled with the absence of specialised predators. There is,
therefore, phenotypic overdispersion and higher functional diversity in cave species when
compared to surface ones. This higher functional diversity results in better efficiency in
resource use, but also in lower resilience of ecological processes. In the second chapter, we
tried to understand the processes underlying patterns of subterranean biodiversity and its
consequences, because species do not occur in all caves or habitat patches where their
occurrences are expected. We looked for the species absences, known as the dark diversity,
for estimation of how much of the habitat-specific regional species pool is realised within
each local cave community. We tested whether the species were absent because of their
functional attributes and tried to understand the relative importance of determinants of
cave biodiversity using local-regional regression models. Our results indicated that the
occurrence of the species is far from its potential, considering habitat availability and
ecological requirements. We found no relationship between species absences and functional
traits but this is possibly an artifact of the low species number and low co-occurrences of
isopods. For the same reason the regression models did not fit in the local-regional
relationship. Differences between caves and regions possibly results from the amount of
microhabitats, resource inputs and historical factors and, from a conservation perspective,
the caves with higher completeness deserve attention, because they may be a source of
migratory individuals to other areas in the vicinity. In the third chapter we compiled the
current state of knowledge of oniscidean fauna in Brazilian caves by listing the described
species and adding several new records from our own surveys. Among these, certainly new
species will be identified. We also addressed the need of validation of the new species and
identification of the unrecognized ones by proper taxonomic research, as any delay may
yield loss of biodiversity.