Abstract
Background. Background matching, as a camouflage strategy, is one of the most outstanding examples of adaptation, where little error or mismatch means high vulnerability to predation. It is assumed that the interplay of natural selection and adaptation are the main evolutionary forces shaping the great diversity of phenotypes observed in mimicry; however, there may be other significant processes that intervene in the development of mimicry such as phenotypic plasticity. Based on observations of background mismatching during reproduction events of egg-cowries, sea snails of the family Ovulidae that mimic the octocoral where they inhabit, we wondered if they match the host species diversity. Using observations in the field and molecular systematics, we set out to establish whether the different egg-cowrie color/shape polymorphisms correspond to distinct lineages restricted to specific octocoral species.Methods. Collection and observations of egg-cowries and their octocoral hosts were done using SCUBA diving between 2009 and 2012 at two localities in the Tropical Eastern Pacific (TEP), Malpelo Island and Cabo Corrientes (Colombia). Detailed host preference observations were done bi-annually at Malpelo Island. We analyzed the DNA sequence of the mitochondrial genes COIand 16S rDNA, extensively used in phylogenetic and DNA barcoding studies, to assess the evolutionary relationship among different egg-cowrie colorations and morphologies.Results. No genetic divergence among egg-cowries associated to different species of the same octocoral genus was observed based on the two mitochondrial genes analyzed. For instance, all egg-cowrie individuals from the two sampled localities observed on 8 different Pacifigorgia-Eugorgia species showed negligible mitochondrial divergence yet large morphologic divergence, which suggests that morphologies belonging to at least two sea snail species, Simnia avena(=S. aequalis) and Simnialena rufa, can cross-fertilize.Discussion. Our study system comprised background-matching mimicry, of the masquerade type, between egg-cowries (Simnia/Simnialena) and octocorals (Pacifigorgia/Eugorgia/Leptogorgia). We observed mimicry mismatches related to fitness trade-offs, such as reproductive aggregations vs. vulnerability against predators. Despite the general assumption that coevolution of mimicry involves speciation, egg-cowries with different hosts and colorations comprise the same lineages. Consequently, we infer that there would be significant tradeoffs between mimicry and the pursuit of reproductive aggregations in egg-cowries. The findings of this study not only contribute to the understanding of the evolution of mimicry in egg-cowries, a poorly studied group of marine gastropods, but also to the development of a new biologically meaningful board game that could be implemented as a learning tool.
Highlights
Background matching, as a camouflage strategy, is one of the most outstanding examples of adaptation, where little error or mismatch means high vulnerability to predation
The findings of this study contribute to the understanding of the evolution of mimicry in egg-cowries, a poorly studied group of marine gastropods, and to the development of a new biologically meaningful board game that could be implemented as a learning tool. 60 Key words: Masquerade camouflage, mimicry, octocoral, Pacifigorgia, Neosimnia, Simnia avena, Simnialena rufa, Tropical Eastern Pacific, Chocó, Cabo Corrientes, Malpelo Island, Colombia, evolution games, mitochondrial DNA. 64 Background 65 66 Mimicry provides some of the most spectacular outcomes of adaptation and evolution
The case of camouflage strategy exhibited by egg-cowries is a clear example of adaptive resemblance (Starrett, 1993), and it can be classified as a kind of ‘masquerade’. It is a background matching mimicry where the subject is slightly different to the background but if it is only glimpsed at, it is not recognized as an edible subject different from the background (Endler, 2006; Stoddard, 2012). This is the case of the ovulids genera Simnia and Simnialena associated to octocorals of the genera Pacifigorgia, Eugorgia, and Leptogorgia at the Tropical Eastern Pacific-TEP (Sánchez, 2013). 94 Octocorals comprise some of the most conspicuous benthic organisms at rocky infralittorals 95 throughout the TEP
Summary
Background matching, as a camouflage strategy, is one of the most outstanding examples of adaptation, where little error or mismatch means high vulnerability to predation. It is a background matching mimicry where the subject is slightly different to the background but if it is only glimpsed at, it is not recognized as an edible subject different from the background (Endler, 2006; Stoddard, 2012) This is the case of the ovulids genera Simnia and Simnialena associated to octocorals of the genera Pacifigorgia, Eugorgia, and Leptogorgia at the Tropical Eastern Pacific-TEP (Sánchez, 2013). Morphological differences among species are very subtle, the color pattern at various traits comprises most of the interspecific variation (Breedy & Guzman, 2002) This may impose an adaptive challenge for their associated fauna, since most crustaceans and cowries seen on Pacifigorgia spp. match their colors (J.A. Sánchez, personal observation). Are these specialized ectoparasites matching the host species diversity? The ultimate goal of this game was to facilitate the understanding of evolutionary processes, such as adaptation and natural selection, through a ludic activity that could be implemented in a learning setting
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