Proteomic and morphological divergence in micro-allopatric morphotypes of Melarhaphe neritoides in the absence of genetic differentiation

Abstract

The intertidal zone represents an interesting model system to study adaptation because several ecological factors change abruptly across this area, causing strong divergent selective pressures on a scale of meters. On the Galician shore (NW Spain), 3 species (Littorina saxatilis, Nucella lapillus and Melarhaphe neritoides) show similar adaptation to survive these abrupt changes. The 3 species have independently evolved morphotypes with similar morphological features that occur either in sheltered or exposed environments. However, while in L. saxatilis and N. lapillus the morphotypes are genetically based, no genetic divergence has been found between the morphotypes of M. neritoides. To better understand the extent of divergence between the 2 morphotypes of M. neritoides and the causes of this polymorphism, protein expression patterns of morphotypes collected from 2 Galician localities were studied. Additionally, mtDNA genetic diversity and shell morphometrics were studied for a reference population at Silleiro. A significant and geographically consistent divergence in protein expression was found between morphotypes kept under controlled laboratory conditions for 1 mo. Morphometric analyses showed that the morphotypes maintained the differences in shell shape even after being kept for 15 mo under similar laboratory conditions. No significant genetic differentiation was found between the 2 morphotypes at the mtDNA level despite the high genetic diversity observed. Together, our data suggest phenotypic plasticity as the most likely cause for the morphotypes and provide putative candidate loci that can be further studied for a better understanding of the origin of this adaptive polymorphism.

Selection on hybrids of ecologically divergent ecotypes of a marine snail: the relative importance of exogenous and endogenous barriers

“…CS; U1, degree of globosity; RW1, relative shell aperture) differences between RB and SU ecotypes can only be interpreted in adaptive terms (Carvajal‐Rodríguez et al ., ; Conde‐Padín et al ., , ). Moreover, two other polymorphisms of gastropod species ( Melarhaphe neritoides , Cuña et al ., ; García et al ., ; the dogwhelk Nucella lapillus , Guerra‐Varela et al ., ) affecting shell aperture (RW1) have been detected on the same shores and microhabitats as the RB and SU polymorphism. Hence, exogenous selection acting on shell traits might play an important role in the observed microhabitat distribution.…”

Mitochondrial DNA hyperdiversity and its potential causes in the marine periwinkleMelarhaphe neritoides(Mollusca: Gastropoda)

“…In the present work, we investigate three potential determinants of mtDNA hyperdiversity i.e., μ , selection and N e , in the marine periwinkle Melarhaphe neritoides (Linnaeus, 1758) in the Azores archipelago. Melarhaphe neritoides is an intertidal gastropod that shows signatures of mtDNA hyperdiversity (see data in García et al, 2013 ). It is a small (shell up to 11 mm) temperate species ( Lysaght, 1941 ), in which the sedentary adults produce pelagic egg capsules and long-lived planktonic larvae with high dispersal potential during 4–8 weeks until settlement ( Cronin, Myers & O’riordan, 2000 ; Fretter & Manly, 1977 ; Lebour, 1935 ).…”

Peer Review #1 of "Mitochondrial DNA hyperdiversity and its potential causes in the marine periwinkle Melarhaphe neritoides (Mollusca: Gastropoda) (v0.1)"

“…µ, selection and N e , in the marine periwinkle Melarhaphe neritoides (Linnaeus, 1758) in the Azores archipelago. Melarhaphe neritoides is an intertidal gastropod that shows signatures of mtDNA hyperdiversity (see data in García et al 2013). It is a small (shell up to 11 mm) temperate species (Lysaght 1941), in which the sedentary adults produce pelagic egg capsules and long-lived planktonic larvae with high dispersal potential during 4-8 weeks until settlement (Cronin et al 2000;Fretter & Manly 1977;Lebour 1935).…”

“…It is a small (shell up to 11 mm) temperate species (Lysaght 1941), in which the sedentary adults produce pelagic egg capsules and long-lived planktonic larvae with high dispersal potential during 4-8 weeks until settlement (Cronin et al 2000;Fretter & Manly 1977;Lebour 1935). Melarhaphe neritoides is widely distributed throughout Europe (Fretter & Graham 1980), where it shows a remarkable macrogeographic population genetic homogeneity (inferred from allozyme data) (Johannesson 1992), though locally in Spain it displays huge amounts of mtDNA COI diversity in terms of a large numbers of polymorphic sites (S = 16 %), a very high haplotype diversity (Hd = 0.998) and a very high nucleotide diversity (π = 0.019) (García et al 2013). We studied mtDNA diversity of M.…”