Lack of evidence for reproductive isolation among ecologically specialised lycaenid butterflies

Abstract

Abstract. 1. The evolution of reproductive isolation between recently diverged or incipient species is a critical component of speciation and a major focus of speciation models. In phytophagous insects, host plant fidelity (the habit of mating and ovipositing on a single host species) can contribute to assortative mating and reproductive isolation between populations adapting to alternative hosts. The potential role of host plant fidelity in the evolution of reproductive isolation was examined in a pair of North American blue butterfly species, Lycaeides idas and L. melissa.2. These species are morphologically distinct and populations of each species utilise different host plants; however they share 410 bp haplotypes of the mitochondrial cytochrome oxidase subunit I (COI) gene, indicating recent divergence.3. Some populations using native hosts exhibited strong fidelity for their natal host plant over the hosts used by nearby populations. Because these butterflies mate on or near the host plant, the development of strong host fidelity may create reproductive isolation among populations on different hosts and restrict gene flow.4. Tests of population differentiation using allozyme allele frequency data did not provide convincing evidence of restricted gene flow among populations. Based on morphological differences, observed ecological specialisation, and the sharing of genetic markers, these butterflies appear to be undergoing adaptive radiation driven at least partially by host shifts. Neutral genetic markers may fail to detect the effects of very recent host shifts in these populations due to gene flow and/or the recency of divergence and shared ancestral polymorphism.

Developmental Plasticity, Genetic Differentiation, and Hypoxia-induced Trade-offs in an African Cichlid Fish

“…The rearing experiment on P. multicolor under high-and low-oxygen indicates that genetic components to trait divergence exist among populations, and that this trait divergence seems to be adaptive. Thus, interestingly, in this system evolutionary divergence in ecologically important traits seems to occur in the face of high gene flow, which has also been shown for other studies in natural systems (e.g., [66][67][68][69]). …”

Host plants and immatures as mate-searching cues in Heliconius butterflies

“…Measuring to what extent host plants are used as matesearching cues is then relevant to understanding how such evolutionary processes have been facilitated by this interaction. Host plant fidelity, or the tendency of phytophagous insects to mate and oviposit in their host plants, has facilitated ecological speciation in this group (Gilbert 1978;Feder 1998;Schluter 2001;Ores & Mallet 2002;Cocroft et al 2008), and could have led to the diversification of at least three genera of lycaenid butterflies (Pratt 1994;Nice & Shapiro 2001;Nice et al 2002;Forister 2005;Gompert et al 2006). Thus, much remains to be done to assess the incidence and impact of the use of plant cues in male mate-searching behaviour in butterflies, and evaluate its importance to their evolution and diversification.…”

Dynamic patterns of adaptive radiation

“…Similar observations are often made in natural populations. For example, blue butterfly species Lycaeides idas and Lycaeides melissa utilize different hosts and have diverged significantly in morphology, yet show no differentiation in neutral markers (35).…”