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The
California Hotspots Project: identifying
regions of rapid diversification of mammals.
University of
California Museum of Vertebrate Zoology
The high rate of
anthropogenic impact on natural systems
mandates protection of the evolutionary
processes that generate and sustain
biological diversity. Environmental drivers
of diversification include spatial
heterogeneity of abiotic and biotic agents
of divergent selection, features that
suppress gene flow, and climatic or
geological processes that open new niche
space. To explore how well such proxies
perform as surrogates for conservation
planning, we need first to map areas with
rapid diversification -'evolutionary
hotspots'. Here we combine estimates of
range size and divergence time to map
spatial patterns of neo-endemism for mammals
of California, a global biodiversity
hotspot. Neo-endemism is explored at two
scales: (i) endemic species, weighted by the
inverse of range size and mtDNA sequence
divergence from sisters; and (ii) as a
surrogate for spatial patterns of phenotypic
divergence, endemic subspecies, again using
inverse-weighting of range size. The
species-level analysis revealed foci of
narrowly endemic, young taxa in the central
Sierra Nevada, northern and central coast,
and Tehachapi and Peninsular Ranges. The
subspecies endemism-richness analysis
supported the last four areas as hotspots
for diversification, but also highlighted
additional coastal areas (Monterey to north
of San Francisco Bay) and the Inyo Valley to
the east. We suggest these hotspots reflect
the major processes shaping mammal
neo-endemism: steep environmental gradients,
biotic admixture areas, and areas with
recent geological/climate change.
Anthropogenic changes to both environment
and land use will have direct impacts on
regions of rapid divergence. However,
despite widespread changes to land cover in
California, the majority of the hotspots
identified here occur in areas with
relatively intact ecological landscapes. The
geographical scope of conserving
evolutionary process is beyond the scale of
any single agency or nongovernmental
organization. Choosing which land to closely
protect and/or purchase will always require
close coordination between agencies.
