Genetic and morphological differentiation patterns between sister species: the case of Onthophagus taurus and Onthophagus illyricus (Coleoptera, Scarabaeidae)

Abstract

The present study investigated the morphological and genetic differentiation pattern between two sympatric dung beetle sister species, Onthophagus taurus and Onthophagus illyricus . The geometric morphometric approach coupled with the use of molecular markers allowed examination of the nature of interspecific relationships and an outline of the evolutionary and geographical processes that might have led to interspecific differentiation and the present-day partial sympatric and syntopic pattern of distribution. Geometric morphometrics failed to discrimininate the two species on the ground of external morphological traits, but revealed interspecific differences when the shape of the primary sexual traits was taken into account. The use of two different molecular markers (cytochrome oxidase subunit I gene and amplified fragment-length polymorphism) demonstrates that the two species are genetically well differentiated, forming two distinguishable lineages probably diverged during the Pliocene by allopatric speciation. No evidence of past or recent introgression and no support for hybridization were found, suggesting that sympatry was established subsequently, when speciation was accomplished. Both molecular markers and genital shape indicate that phenotypically intermediate individuals, despite their ambiguous appearance, are members of O. illyricus species rather than hybrids.

Trade-off between horns and other functional traits in two Onthophagus species (Scarabaeidae, Coleoptera)

“…Previous studies showed that head shape varies in relation to horn size Pizzo et al 2006b), which was interpreted as a balancing static system compensating barycentre backing due to horn protrusion in major males. The observed shape modifications also confer a relatively large and solid appearance on major males, which is likely to be advantageous in aggressive encounters.…”

“…If the evolution of some kind of compensation has the ability to reduce the costs associated with ornament development, then sexual selection may allow further exaggeration of ornaments over evolutionary time (Husak and Swallow 2011). It is also known that males bearing longer horns undergo morphological changes that confer higher success in male-male competition (Otte and Staymen 1979;Okada and Miyatake 2004;Okada et al 2007;Okada and Miyatake 2009;Pizzo et al 2006b). After initial contact, fighting Onthophagus males assume a typical position with the head and thorax held low, the abdomen held high, and the forelegs braced against the tunnel walls (Moczek and Emlen 2000).…”

Evolution isolierter Teilpopulationen der Laubholz-Säbelschrecke Barbitistes serricauda (FABRICIUS 1798)

“…Die ermittelten Werte des Fixation Index (F ST ) nach Wright aus der AFLPAnalyse liegen für die Populationen von B. serricauda mit 0,2486 unterhalb des Wertes von 0,504, den Pizzo et al (2006) Ursachen für die Tatsache, dass genetische Unterschiede zwischen isolierten Populationen nicht in einen Zusammenhang mit ihrer räumlichen Distanz gesetzt werden können, sind zum einen in einem mangelnden genetischen Austausch und zum anderen in einer in kleinen Populationen auftretenden genetischen Drift zu suchen. Eine Zunahme der genetischen Differenz zwischen Teilpopulationen durch Isolation, die allerdings bei der Wintermotte Operophtera brumata mit einer Abnahme genetischer Differenzierung innerhalb untersuchter Teilpopulationen einhergeht, wurde von Van Dongen et al (1998) beschrieben.…”

The First Morphometric Study of the Horn Morphological Pattern in a Geotrupidae: The Case of the Dor BeetleCeratophyus rossiiJekel, 1865

“…The developmental mechanisms of horns and their intra and interspecific expression patterns are well studied especially in Scarabaeidae: within this family, due to its large number of species and its morphological variability, Onthophagus is the most studied genus (Emlen, 1997;Emlen and Nijhout, 1999;Emlen et al, 2005;Moczek, 2011;Palestrini et al, 2000;Pizzo et al, 2006aPizzo et al, , b, 2012Macagno et al, 2009Macagno et al, , 2011a. Despite the wealth of studies on the Scarabaeidae, the horn expression pattern of the Geotrupidae, to our knowledge, has never been investigated.…”