Experimental evolution in sympatry leads to higher growth rates, but does not alleviate the costs of competition and reproductive interference
Year: 2026
Type: preprint
Abstract: Organisms often exert strong fitness costs upon individuals from other species that either compete for the same resources or that interact with them via reproductive interference. Therefore, evolution in sympatry is expected to lead to the alleviation of such interactions, ultimately facilitating coexistence. However, only few studies have tested the effect of evolution on competition and reproductive interference simultaneously. To fill this gap, we measured the strength of these interactions after 20 generations of experimental evolution of two incipient spider mite species, Tetranychus urticae and T. cinnabarinus in allopatry or in sympatry, in a homogeneous environment. We found that most responses after evolution in sympatry were transient, suggesting an important role of fluctuating selection. In particular, we found higher intrinsic growth rates of both species in sympatry, but only at specific time points, which differ between T. urticae and T. cinnabarinus. This came at a cost for T. urticae, which suffered from increased sensitivity to interspecific competition and lower ability to induce reproductive interference on T. cinnabarinus, suggesting a growth-competition trade-off. Other negative correlations among traits underlying trophic and sexual interactions were also found. Together, such constraints may hamper species divergence, which is compatible with the lack of significant changes in the probability of coexistence between the two species after evolving with heterospecifics. Possibly, a more complex environment may be necessary to enable trait changes facilitating coexistence.
Source: HAL
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7161795082