Data from: Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta-analysis

Habitat loss and fragmentation are among the biggest threats to
biodiversity. Anthropogenic habitat fragmentation leads to small and
isolated remnant plant and animal populations. The combination of
increased random genetic drift, inbreeding, and reduced gene flow may
substantially reduce genetic variation of remnant populations. However,
the magnitude of these responses may depend on several poorly understood
factors including organism group, habitat type of both the fragment and
the surrounding matrix, life‐history traits, and time since fragmentation.
We compiled data for 83 plant and 52 animal species and conducted a
meta‐analysis following best practices to evaluate how these factors
mediate the effects of anthropogenic habitat fragmentation. We calculated
206 effect sizes as correlations between one of four measures of
population‐level genetic diversity and fragment area. All analyses were
repeated using models of increasing complexity (traditional random‐effects
models, multilevel models accounting for non‐independent data, and
multilevel models additionally correcting for phylogenetic relatedness).
We confirmed that anthropogenic habitat fragmentation has overall negative
effects on genetic diversity of organisms. Our meta‐analysis shows,
however, that plant species responded in general stronger to fragmentation
than animal species and that the largest negative impacts of fragmentation
occurred in tropical and temperate forest fragments, surrounded by a
non‐forest matrix. In contrast, we found only weak responses in non‐forest
fragments. Genetic diversity measured as mean number of alleles (A) showed
the strongest response to fragmentation. Expected heterozygosity (He) and
percentage of polymorphic loci (PLP) showed similar but weaker responses.
In contrast, our meta‐analysis indicated that inbreeding (Fis) was not
measurably affected by anthropogenic habitat fragmentation. Additionally,
our models revealed that effects on genetic diversity became stronger with
age of fragments: We found significant negative responses for fragments
older than 50 yr but not for those more recently isolated. Our
meta‐analyses also showed that currently animals are underrepresented in
the literature on genetic effects of anthropogenic fragmentation, as are
certain geographical regions and habitat types. We expect that future
field studies using state‐of‐the‐art approaches will provide further
evidence of negative genetic effects, which may reinforce the here
reported patterns, even for groups not yet studied.