Nuclear and mitochondrial sequences confirm complex colonization patterns and clear species boundaries for flightless weevils in the Galápagos archipelago

Abstract

Nuclear sequence data were collected from endemic Galápagos species and an introduced close relative, and contrasted with mitochondrial DNA sequences, continuing investigation into the colonization history and modes of diversification in the weevil genus Galapaganus. The current combined phylogeny together with previously published penalized likelihood age estimates builds a complex picture of the archipelago's colonization history. The present reconstruction relies on submerged platforms to explain the early divergence of the young southern Isabela endemics or the Españ ola or San Cristobal populations. Diversity is later built through inter-island divergence starting on older islands and continuing on two simultaneous tracks towards younger islands. The amount of diversity generated through intra-island processes is skewed towards older islands, suggesting that island age significantly influences diversity. Phylogenetic concordance between nuclear and mitochondrial datasets and well-supported monophyletic species in mitochondrial derived topologies appear to reject the possibility of inter-species hybridization. These clear species boundaries might be related to the tight host associations of adult weevils in discrete ecological zones. If shared hosts facilitate hybridization, then host-or habitat-promoted divergences could prevent it, even in the case of species that share islands, since the altitudinal partitioning of habitats minimizes range overlap.

Nuclear-Mitochondrial Barcoding Exposes the Global Pest Western Flower Thrips (Thysanoptera: Thripidae) as Two Sympatric Cryptic Species in Its Native California

“…Approximately 10% of accepted animal species are known to hybridize (Mallet 2007), and mitochondrial introgression is commonly cited as evidence for such hybridization (Shaw 2002, Bachtrog et al 2006, Linnen and Farrell 2007, Kawakami et al 2007, Gompert et al 2008, Nevado et al 2009, Spinks and Shaffer 2009, Kemppainen et al 2009). Instead, the complete linkage diseqilibrium displayed by rDNA and mtDNA loci in our specimens is indicative of two fully reproductively isolated species (Mallet 1995, Bensch et al 2004, Monaghan et al 2005, Lukhtanov and Shapoval 2008, Gaines et al 2009, Sequeira et al 2009). …”

“…If a population is totally panmictic, across a sample of individuals, regardless of levels of sequence divergence, we expect to see complete mixing of nuclear and mitochondrial barcodes. However, if individuals in that population do not interbreed freely (i.e., cryptic species), then given a sample that avoids any potential effect of genetic relatedness (e.g., one that is too small and/or from a single location) (Lukhtanov and Shapoval 2008), we expect to see congruent partitioning in the "signals" read from nuclear and mitochondrial barcodes (Bensch et al 2004, Monaghan et al 2005, Lukhtanov and Shapoval 2008, Gaines et al 2009, Sequeira et al 2009). In this study, we used a nuclear and a mitochondrial gene, but separate nuclear genes that are known to occur on different chromosomes may be equally effective.…”

Phylogeny of the tribe Naupactini (Coleoptera: Curculionidae) based on morphological characters

“…The taxonomic works of later authors (Kuschel, , , ; Hustache, ; Voss, ; Bordón, , ) contributed to knowledge the diversity of the tribe Naupactini in the Neotropics, and the revisions and phylogenetic analyses published by other specialists have shed light on the relationships of several Neotropical genera and species (Lanteri, ,, , ; Lanteri & O'Brien, ; Lanteri & Morrone, , ; Lanteri & Díaz, ; Normark & Lanteri, ; Sequeira et al ., , ,; Scataglini et al ., ; del Río et al ., , ; Rosas–Echeverría et al ., ; Lanteri & del Río, ). Nevertheless, several problems still remain unresolved.…”

Population genomics and geographical parthenogenesis in Japanese harvestmen (Opiliones, Sclerosomatidae, Leiobunum)

“…Mitonuclear concordance may be indicative of a number of speciation mechanisms (Larmuseau, Raeymaekers, Hellemans, Van Houdt, & Volckaert, ; Toews & Brelsford, ), including hybridization and incomplete lineage sorting (Denton, Kenyon, Greenwald, & Gibbs, ; Gompert, Forister, Fordyce, & Nice, ; Zakas, Jones, & Wares, ). Increasing concordance between the mitochondrial and nuclear genomes may signal co‐adaptation of the genomes (Hadjivasiliou, Pomiankowski, Seymour, & Lane, ), but also implicates a decrease in dispersal and/or genetic exchange (Fang, Chen, Jiang, Chen, & Qiao, ; Sequeira, Sijapati, Lanteri, & Albelo, ; Simon, Delmotte, Rispe, & Crease, ), as may be seen in organisms that reproduce facultatively or obligately through parthenogenesis (Paczesniak et al., ; Thielsch, Brede, Petrusek, de Meester, & Schwenk, ) or other rare fertilization patterns (Eyer, Leniaud, Tinaut, & Aron, ; Hedtke & Hillis, ; Schaschl, Tobler, Plath, Penn, & Schlupp, ).…”