Genotypic and phenotypic variation in transmission traits of a complex life cycle parasite

Katja‐Riikka Louhi,Jukka Jokela,Christian Rellstab,Anssi Karvonen

doi:10.1002/ece3.621

Abstract

Characterizing genetic variation in parasite transmission traits and its contribution to parasite vigor is essential for understanding the evolution of parasite life-history traits. We measured genetic variation in output, activity, survival, and infection success of clonal transmission stages (cercaria larvae) of a complex life cycle parasite (Diplostomum pseudospathaceum). We further tested if variation in host nutritional stage had an effect on these traits by keeping hosts on limited or ad libitum diet. The traits we measured were highly variable among parasite genotypes indicating significant genetic variation in these life-history traits. Traits were also phenotypically variable, for example, there was significant variation in the measured traits over time within each genotype. However, host nutritional stage had no effect on the parasite traits suggesting that a short-term reduction in host resources was not limiting the cercarial output or performance. Overall, these results suggest significant interclonal and phenotypic variation in parasite transmission traits that are not affected by host nutritional status.

Highlights

Studies on life-history traits let us expect that many of the phenotypic differences observed among individuals have a genetic basis (Roff 1992; Stearns 1992)
In this study we focus on the variation in life-history traits of trematodes, a group of parasites with a complex life cycle typically including three transmission steps, an endothermic final host, a mollusc first intermediate host, and an invertebrate or vertebrate second intermediate host
Results of weeks 1 and 2 were analyzed together, using week as a factor, to test for significant differences in the traits between the treatments and weeks. These analyses were done with linear-mixed models (LMMs) and a generalized linear-mixed model (GLMM), respectively

Summary

Introduction

Studies on life-history traits let us expect that many of the phenotypic differences observed among individuals have a genetic basis (Roff 1992; Stearns 1992). There are no reasons to assume that parasite life-history traits would be an exception of this pattern (Poulin 1996), evolution of parasite life-history traits is less studied using the concepts of life-history theory. This may be surprising because understanding the processes that maintain genetic variation in transmission-related traits is fundamental for our understanding of how parasite transmission evolves. Parasites that reproduce clonally at some stage of their life cycle provide interesting opportunities to test how much of the phenotypic variation has a genetic basis.

Objectives

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Results

Conclusion