Discovery of long-distance gamete dispersal in a lichen-forming ascomycete.

Cecilia Ronnås,Otso Ovaskainen,Silke Werth,Tord Snäll,Gergely Várkonyi,Christoph Scheidegger

doi:10.1111/nph.14714

Abstract

Summary Accurate estimates of gamete and offspring dispersal range are required for the understanding and prediction of spatial population dynamics and species persistence. Little is known about gamete dispersal in fungi, especially in lichen‐forming ascomycetes. Here, we estimate the dispersal functions of clonal propagules, gametes and ascospores of the epiphytic lichen Lobaria pulmonaria.We use hierarchical Bayesian parentage analysis, which integrates genetic and ecological information from multiannual colonization and dispersal source data collected in a large, old‐growth forest landscape.The effective dispersal range of gametes is several hundred metres to kilometres from potential paternal individuals. By contrast, clonal propagules disperse only tens of metres, and ascospores disperse over several thousand metres.Our study reveals the dispersal distances of individual reproductive units; clonal propagules, gametes and ascospores, which is of great importance for a thorough understanding of the spatial dynamics of ascomycetes. Sexual reproduction occurs between distant individuals. However, whereas gametes and ascospores disperse over long distances, the overall rate of colonization of trees is low. Hence, establishment is the limiting factor for the colonization of new host trees by the lichen in old‐growth landscapes.

Highlights

Dispersal is a process of fundamental importance for the spatial dynamics, evolution and migration of populations (Bullock et al, 2002; Kokko & Lopez-Sepulcre, 2006)
The aim of this study was to fit the mathematical functions describing the dispersal of clonal propagules, gametes and ascospores of the lichen-forming ascomycete L. pulmonaria (Peltigerales)
1⁄4byRZ01(dz)ð=d z(d)2pd, Þ2pd dd and 1⁄41 they To allow for the possibility of both short- and long-distance dispersal, we modelled all dispersal functions z(d) using the bivariate Student t distribution with scale matrix a2I and shape parameter m

Summary

Introduction

Dispersal is a process of fundamental importance for the spatial dynamics, evolution and migration of populations (Bullock et al, 2002; Kokko & Lopez-Sepulcre, 2006). Clonal reproduction produces fairly large diaspores which enhances short-distance dispersal, whereas sexual reproduction produces small diaspores enhancing long-distance dispersal (Tackenberg, 2003; Scheidegger & Werth, 2009; Werth et al, 2014). These two dispersal modes with different propagule sizes and resulting dispersal distances have large effects on local population growth, pattern and rate of spatial spread, metapopulation dynamics and genetic diversity (Snyder & Chesson, 2003; Soons & Ozinga, 2005; Zhang & Zhang, 2007; Marco et al, 2011; Johansson et al, 2012). The success of sexual dispersal depends on the availability of breeding partners, either by direct contact between neighbouring individuals or thanks to the dispersal of mobile gametes

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