Fast life history traits promote invasion success in amphibians and reptiles

Abstract

Competing theoretical models make different predictions on which life history strategies facilitate growth of small populations. While 'fast' strategies allow for rapid increase in population size and limit vulnerability to stochastic events, 'slow' strategies and bet-hedging may reduce variance in vital rates in response to stochasticity. We test these predictions using biological invasions since founder alien populations start small, compiling the largest dataset yet of global herpetological introductions and life history traits. Using state-of-the-art phylogenetic comparative methods, we show that successful invaders have fast traits, such as large and frequent clutches, at both establishment and spread stages. These results, together with recent findings in mammals and plants, support 'fast advantage' models and the importance of high potential population growth rate. Conversely, successful alien birds are bet-hedgers. We propose that transient population dynamics and differences in longevity and behavioural flexibility can help reconcile apparently contrasting results across terrestrial vertebrate classes.

Keywords: Amphibians; biological invasions; comparative analyses; invasion biology; invasive species; life history theory; population dynamics; population growth; reptiles; transient dynamics.

Figure 1

The success of amphibians and reptiles at each stage of the invasion pathway: introduction, establishment and spread. (a) The sample size and number of species that succeed or fail at each stage of invasion, including species for which no reliable judgement can be made (indicated as ‘?’). (b) Posterior distributions of the parameter estimates (β) of life history traits and introduction effort at each stage of invasion. Traits are: snout‐vent length (SVL, amphibians), body mass (BM, reptiles), egg size (ES, amphibians), hatchling mass (HM, reptiles), clutch size (CS), clutches per year (CY, reptiles only), age at sexual maturity (SM), reproductive lifespan (RL), parity (PA, oviparous = 0, viviparous = 1, reptiles only) and introduction effort (IE). Posterior distributions are centred on zero (dashed line) when they have negligible influence on the probability of success and are substantially shifted from zero when they are influential. In (c) summary of results by stage of invasion in both classes.

Figure 2

Posterior distribution of heritability (h ²) at each stage of the invasion pathway in amphibians and reptiles.