Evolutionary Speed of Species Invasions

Abstract

Successful invasion may depend of the capacity of a species to adjust genetically to a spatially varying environment. This research modeled a species invasion by examining the interaction between a quantitative genetic trait and population density. It assumed: (I) a quantitative genetic trait describes the adaptation of an individual to its local ecological conditions; (2) populations far from the local optimum grow more slowly than those near the optimum; and (3) the evolution of a trait depends on local population density, because differences in local population densities cause asymmetrical gene flow. This genetics-density interaction determined the propagation speed of populations. Numerical simulations showed that populations spread by advancing as two synchronic traveling waves, one for population density and one for trait adaptation. The form of the density wave was a step front that advances homogenizing populations at their carrying capacity; the adaptation wave was a curve with finite slope that homogenizes populations at full adaptation. The largest speed of population expansion, for a dimensionless analysis, corresponded to an almost homogeneous spatial environment when this model approached an ecological description such as the Fisher-Skellam's model. A large genetic response also favored faster speeds. Evolutionary speeds, in a natural scale, showed a wide range of rates that were also slower compared to models that only consider demographics. This evolutionary speed increased with high heritability, strong stabilizing selection, and high intrinsic growth rate. It decreased for steeper environmental gradients. Also indicated was an optimal dispersal rate over which evolutionary speed declined. This is expected because dispersal moves individuals further, but homogenizes populations genetically, making them maladapted. The evolutionary speed was compared to observed data. Furthermore, a moderate increase in the speed of expansion was predicted for ecological changes related to global warming.

Understanding and monitoring the consequences of human impacts on intraspecific variation

“…In addition, phenotypic and genetic changes have been observed in many introduced species and the native species with which they interact (Hendry et al., 2008; Mooney & Cleland, 2001). Although the extent to which these changes are adaptive is not always certain (Colautti & Lau, 2015), evolution in introduced species is predicted to influence the rate, extent, and impact of invasions (García‐Ramos & Rodríguez, 2002; Vázquez‐Domínguez, Suárez‐Atilano, Booth, González‐Baca, & Cuarón, 2012). Thus, novel selective pressures can lead to evolutionary changes in both native and invasive species that then influence the abundance of those species, with expected further consequences for intraspecific variation.…”

Increased genetic variation and evolutionary potential drive the success of an invasive grass

“…Despite these detrimental effects, little is known about the evolutionary mechanisms that permit geographic range expansion and evolution of invasiveness in introduced species (4,5). Theoretical models of species geographic range predict that species boundaries will be static when peripheral populations lack heritable phenotypic variation (6) or cannot adapt to local environmental conditions because of continuous gene flow from central populations (7,8). Yet, many introduced species have expanding range margins and thus can provide insights into important evolutionary processes that drive adaptation and range expansion (9,10).…”

Interaction Between Fournder Effect and Selection During Biological Invasion in an Aquatic Plant

“…Sexual reproduction generates genotypic diversity, which may increase the rate of adaptive evolution during expansion into new habitats (Reznick and Ghalamobor 2001;Kaltz and Bell 2002;García-Ramos and Rodriguez 2002). The seeds produced by sexual reproduction are also more likely to participate in long-distance colonization than vegetative clonal propagules, which are often larger, more vulnerable to desiccation, lack mechanisms for dispersal and dormancy, and therefore have less capacity for dispersal (Ashton and Mitchell 1989;Starfinger and Stö cklin 1996;Lambrinos 2001;Eckert 2002).…”