Reduced gene ﬂow in a vulnerable species reﬂects two centuries
of habitat loss and fragmentation
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220 Australia
School of Biological Sciences, Monash University, Melbourne, Victoria 3168 Australia
Department of Ecology Environment and Evolution, School of Life Sciences, La Trobe University, Bundoora, Victoria 3083 Australia
Arthur Rylah Institute for Environmental Research, Heidelberg, Victoria 3084 Australia
School of Applied and Biomedical Sciences, Federation University Australia, Churchill, Victoria 3842 Australia
Citation: Stevens, K., K. A. Harrisson, F. E. Hogan, R. Cooke, and R. H. Clarke. 2018. Reduced gene ﬂow in a vulnerable
species reﬂects two centuries of habitat loss and fragmentation. Ecosphere 9(2):e02114. 10.1002/ecs2.2114
Understanding the effects of landscape modiﬁcation on gene ﬂow of fauna is central to inform-
ing conservation strategies that promote functional landscape connectivity and population persistence. We
explored the effects of large-scale habitat loss and fragmentation on spatial and temporal patterns of gene
ﬂow in a threatened Australian woodland bird: the Grey-crowned Babbler Pomatostomus temporalis. Using
microsatellite data, we (1) investigated historical (i.e., pre-fragmentation) and contemporary (i.e., post-
fragmentation) levels of gene ﬂow among subpopulations and/or regions, (2) identiﬁed ﬁrst-generation
migrants and likely dispersal events, (3) tested for signatures of genetic bottlenecks, (4) estimated contem-
porary and historical effective population sizes, and (5) explored the relative inﬂuences of drift and migra-
tion in shaping contemporary population structure. Results indicated that the functional connectivity of
landscapes used by the Grey-crowned Babbler is severely compromised in the study area. The proportion
of individuals that were recent immigrants among all subpopulations were low. Habitat fragmentation has
led to a clear division between subpopulations in the east and west, and the patterns of gene ﬂow exchange
between these two regions have changed over time. The effective population size estimates for these two
regions are now well below that required for long-term population viability (N
< 100). Demographic
history models indicate that genetic drift was a greater inﬂuence on subpopulations than gene ﬂow, and
most subpopulations show signatures of bottlenecks. Translocations to promote gene ﬂow and boost
genetic diversity in the short term and targeted habitat restoration to improve landscape functional
connectivity in the long term represent promising conservation management strategies that will likely have
beneﬁts for many other woodland bird species.
Key words: ancestry; bottleneck; functional connectivity; region; subpopulation.
Received 18 September 2017; revised 7 December 2017; accepted 10 January 2018. Corresponding Editor: Alice W. Boyle.
Copyright: © 2018 Stevens et al. This is an open access article under the terms of the Creative Commons Attribution
License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
In memory of Nigel Lacey.
Habitat loss and fragmentation have a sub-
stantial inﬂuence on the structure and viability of
animal populations (Hanski et al. 1995, Villard
et al. 1999, Ortego et al. 2015). Landscape-scale
anthropogenic habitat modiﬁcation can fragment
populations into small, isolated subunits that are
at an increased risk of local patch extinction
(Hanski 1998, Saccheri et al. 1998, Fuhlendorf
et al. 2002, Banks et al. 2005). Small populations
lose genetic diversity through random genetic
drift, leaving them vulnerable to the negative
effects of inbreeding and reducing their capacity
to adapt to environmental change (Saccheri et al.
1998, O’Grady et al. 2006, Pavlacky et al. 2012).