A case of reproductive character displacement in female palmate newts (Lissotriton helveticus)

Abstract

Reproductive character displacement is commonly described as larger phenotypic differences between species living in sympatry rather than in allopatry. We investigated this phenomenon on two amphibians found in their contact zone where syntopic and allotopic sites alternate. To test the effect of syntopy with Lissotriton vulgaris on the Lissotriton helveticus phenotype, we studied the morphology of adult males and females while controlling for environmental factors (i.e. land use and flood risk). Using linear mixed-effects models, we found that females of L. helveticus expressed a deeper tail when in the presence of the other species, a pattern consistent with reproductive character displacement. This pattern has been rarely observed in Amphibians. It suggests that male newts incur large mating costs when selecting heterospecific partners. Our study also emphasizes that the evolution of mate recognition systems could occur at a microgeographical scale within a sympatric area. To cite this article: A.

Robustness of newt heads in condition of co-existence: a case of the Carpathian newt and the alpine newt

“…Head shape patterns are present at earlier ontogenetic stages, which means that differences in head shape between species and between clutches may occur in the early development (Adams 2011 ). However, the observed variability may also be closely related to the density and availability of food (De Lisle and Rowe 2015 ) or habitat differences (Sotiropoulos et al 2008 ; Johanet et al 2009 ), which can strongly influence morphological traits. The diets of newt larvae belonging to medium-sized ( I. alpestris ) and small ( L. montandoni ) species are more similar than those of larvae belonging to L. montandoni and Triturus cristatus.…”

“…This means that some traits can be minimised or lost when the geographical ranges of species do not overlap (Brown and Wilson 1956 ; Dayan and Simberloff 2005 ). Changes in characteristics are important, because they reduce intra- and interspecific competition (Vignoli et al 2007 ), and are known to occur in many taxa (Dayan and Simberloff 2005 ), including tailed amphibians (Adams and Rohlf 2000 ; Adams et al 2007 ; Johanet et al 2009 ; De Lisle and Rowe 2015 ). However, competition for food resources may also occur between sexes within the same species (De Lisle and Rowe 2015 ).…”

Widespread introgression does not leak into allotopy in a broad sympatric zone

“…According to our data, introgression was thus common in syntopy but did not leak out into allotopy. The result is striking as allotopic and syntopic sites in the Loire river study area alternate along the valley on a short geographical scale (Johanet et al, 2009b). We may not have had enough power to accurately detect all hybrids as suggested by NEWHY-BRIDS and STRUCTURE output.…”

“…Our current knowledge of the hybridization process between the two species may be strongly biased because of the difficulty in identifying phenotypic hybrids in one sex. In contrast to males that are readily identified by secondary sexual traits, females of each species look alike, and overlap for several traits such as colour pattern of underparts (Johanet et al, 2009b). Thus, female hybrids are difficult to identify and female backcrosses are almost impossible to distinguish from parental species (Naisbit et al, 2003) by morphological criteria alone.…”

“…We also scored the throat pattern by coding '0' for a clear throat (typical of L. helveticus) to '4' for a completely marbled throat (typical of L. vulgaris). These traits are known or likely to discriminate the two species (Griffiths and Mylotte, 1988;Johanet et al, 2009b). Individuals were subsequently released to their original capture sites.…”