Habitat quality or quantity? Changes in niche marginality across 21
species of plant and animal suggest differential responses between
highland and lowland species to past climatic changes
Abstract
Climatic changes can affect species distributions, population abundance,
and evolution. Such organismal responses could be determined by the
amount and quality of available habitats, which can vary independently.
In this study, we assessed changes in habitat quantity and quality
independently to generate explicit predictions of the species’ responses
since the Last Glacial Maximum (LGM) climatic changes. We built
ecological niche models and distribution models for 21 reptile, mammal,
and plant taxa from the Baja California peninsula inhabiting lowland or
highland environments. Geological data suggests the CCSM global
circulation model is a better representation of LGM climate for the Baja
California peninsula. Significant niche divergence was detected for all
clades within species, along with significant differences in niche
breadth and area of distribution between northern and southern clades.
Most clades showed a reduction in distribution area towards LGM.
Further, niche marginality (used as a measure of habitat quality) was
higher during LGM for most clades, except for northern highland species
who experienced improvements in both. Our results suggest that changes
in habitat quantity and quality can affect organismal response
independently. This allows the prediction of genomic signatures
associated with changes in effective population size and selection
pressure that could be explicitly tested to support our models.