Shifts in reproductive assurance strategies and inbreeding costs associated with habitat fragmentation in Central American mahogany.

Martin F Breed,Michael G Gardner,Kym M Ottewell,Carlos M Navarro,Andrew J Lowe

doi:10.1111/j.1461-0248.2012.01752.x

Abstract

The influence of habitat fragmentation on mating patterns and progeny fitness in trees is critical for understanding the long-term impact of contemporary landscape change on the sustainability of biodiversity. We examined the relationship between mating patterns, using microsatellites, and fitness of progeny, in a common garden trial, for the insect-pollinated big-leaf mahogany, Swietenia macrophylla King, sourced from forests and isolated trees in 16 populations across Central America. As expected, isolated trees had disrupted mating patterns and reduced fitness. However, for dry provenances, fitness was negatively related to correlated paternity, while for mesic provenances, fitness was correlated positively with outcrossing rate and negatively with correlated paternity. Poorer performance of mesic provenances is likely because of reduced effective pollen donor density due to poorer environmental suitability and greater disturbance history. Our results demonstrate a differential shift in reproductive assurance and inbreeding costs in mahogany, driven by exploitation history and contemporary landscape context.

Highlights

Forests form key global ecosystems that humans have utilised for millennia, but many have experienced unsustainable exploitation resulting in disrupted ecosystem processes
Regardless of mating system, inbreeding depression is more commonly expressed in more stressful environments (Fox & Reed 2010) and is expected to become more severe as environment-dependent stress increases due to global change (Beaumont et al 2011)
We demonstrate that increased selfing and correlated paternity both negatively impact progeny growth, but that variation in these mating system parameters impacts growth differentially in rainfall-determined seed provenances

Summary

Introduction

Forests form key global ecosystems that humans have utilised for millennia, but many have experienced unsustainable exploitation resulting in disrupted ecosystem processes (e.g. pollination; Fig. 1). Effects of human disturbance (e.g. clearing, selective logging) on tree mating patterns have been well studied (Eckert et al 2010), including numerous neotropical examples (Lowe et al 2005; Ward et al 2005). Both self-compatible and self-incompatible species are expected to experience fitness declines through reduced mate availability with disturbance (Fig. 1, response a). For species within these altered habitats, new shifts in reproductive assurance and fitness costs associated with inbreeding may be observed (Herlihy & Eckert 2002; Kalisz et al 2004)

Methods

Discussion

Conclusion