Warmer seed environments increase germination fractions in Australian winter annual plant species

John M Dwyer,Todd E Erickson

doi:10.1002/ecs2.1497

John M Dwyer, Todd E Erickson

Open Access

https://doi.org/10.1002/ecs2.1497

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Abstract

AbstractClimate can influence plant demographic processes and life stages in different ways, but such details are often ignored in analyses that focus on adult life stages and annual climate averages. In particular, the effects of climate on seeds may be hugely important under climate change. Climate is known to influence seed survival and germination, which in turn can strongly affect population persistence and community dynamics. We investigated climate and other environmental effects on seed viability and germination probabilities of six winter annual plant species persisting in small, isolated habitat fragments in the Mediterranean‐climate region of southwestern Australia. Seeds were collected from southern (cool) and northern (warm) bushland remnants and factorially placed into each location to assess the effects of natural dormancy alleviation via after‐ripening. Seeds were then exposed to cool and warm germination treatments (representing average germination conditions in the two remnants). For five of the six species, seeds from warm maternal populations had higher germination probabilities (or germinated more seeds sooner). Regardless of maternal population, germination probabilities were higher (or germination was more rapid) for seeds that were after‐ripened in the warm remnant for almost all species. For all species, germination was higher (or more rapid) under the warmer germination temperatures. We also found strong microsite effects on seed viability for some species. In the absence of adaptation in dormancy regulation and germination physiology, our results indicate that most of the winter annual species studied will germinate higher fractions of seeds under future climate conditions due to the cumulative effects of warmer maternal, after‐ripening, and germination environments. The fate of isolated populations under climate change may therefore depend strongly on postgermination survival and reproduction to prevent seed bank depletion.

Highlights

Outside of the tropics, Mediterranean-climate ecosystems (MCEs) support the highest levels of vascular plant diversity and endemism in the world (Cowling et al 1996, Kreft and Jetz 2007)
Viability After accounting for background viability proportions, maternal population had a significant v www.esajournals.org effect on the viability of all five species for which seed was collected from both maternal populations
AR environment and microsite had no significant effects on the viability of G. berardiana and P. airoides

Summary

Introduction

Mediterranean-climate ecosystems (MCEs) support the highest levels of vascular plant diversity and endemism in the world (Cowling et al 1996, Kreft and Jetz 2007). Dwyer and Erickson et al 2005), mainly associated with urban and agricultural development (Underwood et al 2009). In these highly fragmented landscapes, the capacity of species to disperse and track preferred climates has been reduced (or eliminated), placing greater importance on local adaptation as a means to prevent local or total extinction (Sala et al 2000, Jump and Penuelas 2005, Loarie et al 2009). Predicting species’ abilities to tolerate or adapt to changing climates is difficult because climate influences different demographic processes and life stages in diverse ways (Keith et al 2008, Donohue et al 2010, Walck et al 2011, Cochrane et al 2015b)

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