Classics: demography versus genetics

16 03 2011

Here’s another short, but sweet Conservation Classic highlighted in our upcoming book chapter (see previous entries on this book). Today’s entry comes from long-time quantitative ecology guru, Russ Lande, who is now based at the Silwood Park Campus (Imperial College London).

© IBL

In an influential review, Lande (1988) argued that

“…demography may usually be of more immediate importance than population genetics in determining the minimum viable size of wild populations”.

It was a well-reasoned case, and was widely interpreted to mean that demographic and ecological threats would provide the ‘killer blow’ to threatened species before genetic factors such as inbreeding and fitness effects of loss of genetic diversity had time to exert a major influence on small population dynamics.

Lande’s paper ignited a fire under the belly of conservation geneticists, and led to a concerted effort to come up with stronger evidence for the role of genetics in elevating extinction risk. This in turn resulted in innovative field experiments (Saccheri et al., 1998), meta-analyses on genetically effective population size (Frankham 1995), studies on the enhanced effect of inbreeding on wild populations (Crnokrak & Roff, 1999), and a pairwise comparison of 170 threatened taxa showing that the majority had indeed suffered from a reduction genetic diversity compared to their non-threatened congeners (Spielman et al., 2004).

The net conclusion is that demographic and genetic changes can work in concert in small populations to threaten their viability and survival (Mills & Smouse, 1994).

CJA Bradshaw, NS Sodhi, WF Laurance, BW Brook

ResearchBlogging.orgLande, R. (1988). Genetics and demography in biological conservation Science, 241 (4872), 1455-1460 DOI: 10.1126/science.3420403


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27 04 2011
Classics: Effective population size ratio « ConservationBytes.com

[…] (Charlesworth & Charlesworth, 1987), genetic hazards were generally considered to be of less consequence to extinction risk than demographic and environmental stochasticity. Frankham (1995) helped overturn this viewpoint, using a meta-analysis to draw together […]

17 03 2011
Simone Vincenzi

Russ Lande is truly one of the greats.

The question is: was the idea about genetics being more important than demography (and ecology) for persistence of small populations before the Lande paper held only by conservation genetists (and that would clearly be easy to understand) or widespread among conservation ecologists?

17 03 2011
CJAB

Pretty safe to assume most believed genetics were of minor, if any importance in extinction dynamics. Clearly we know differently now.

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