DECADAL ACTIVITY PATTERNS IN AN ISOLATED URBAN REPTILE ASSEMBLAGE:
MONITORING UNDER A CHANGING CLIMATE.
Abstract
Aim Determine seasonal, annual and decadal patterns of abundance in
reptile populations and assemblages occupying an isolated urban bushland
remnant Location Bold Park (~338 ha), Perth,
Southwestern Australia Time period 1986-2021 Major taxa studied:
Squamate reptiles Methods Fenced pitfall trapping in four sampling sites
representing different habitats and fire history over the primary
reptile activity period and 35 consecutive years; trapping regime was
modified for the last 28 years. Results The location occurs in one of 35
global biodiversity hotspots and has a Mediterranean climate
experiencing a 15% decline from the century average rainfall over the
last 50 years. Twenty-nine species were recorded, with 16 captured in 32
or more years and accounting for nearly 97% of all captures; the six
most common for 81%. Three taxa became locally extinct. Activity
predominates in warmer and dryer months (October to April), peaking in
November December. Species richness remained relatively constant between
years with around 73% of known taxa captured annually. Assemblage
structure didn’t change when analysing presence/absence data but shifted
through five statistically significantly assemblages analysing relative
abundance data. Over the last 28 years relative abundance was
significantly and positively correlated with annual rainfall residuals
for the three years preceding annual sampling, resulting in significant
changes in total assemblage structure and significantly similar patterns
in four sample sites; presence/absence data indicated minor assemblage
structure changes. Main conclusions Annual species number remained
relatively constant but relative abundance illustrated significant
temporal changes in assemblage structure over decades; presence/absence
did not. The modeled relationship between relative abundance and annual
rainfall residuals for the three years preceding annual sampling is
supported by known ecological responses and reptile demographics within
this Mediterranean climate. Maintenance of urban biodiversity should
consider impacts of a significantly drying climate exacerbating the
extinction debt already inherent in isolated bushland populations.