Genetic and morphological differentiation in Tephritis bardanae (Diptera: Tephritidae): evidence for host-race formation

Abstract

The fruit fly Tephritis bardanae infests flower heads of two burdock hosts, Arctium tomentosum and A. minus. Observations suggest host‐associated mating and behavioural differences at oviposition indicating host‐race status. Previously, flies from each host plant were found to differ slightly in allozyme allele frequencies, but these differences could as well be explained by geographical separation of host plants. In the present study, we explicitly test whether genetic and morphological variance among T. bardanae are explained best by host‐plant association or by geographical location, and if this pattern is stable over a 10‐year period. Populations of A. tomentosum flies differed significantly from those of A. minus flies in (i) allozyme allele frequencies at the loci Pep‐A and Pgd, (ii) mtDNA haplotype frequencies and (iii) wing size. In contrast, geographical location had no significant influence on the variance estimates. While it remains uncertain whether morphometric differentiation reflects genotypic variability or phenotypic plasticity, allozyme and mtDNA differentiation is genetically determined. This provides strong evidence for host‐race formation in T. bardanae. However, the levels of differentiation are relatively low indicating that the system is in an early stage of divergence. This might be due to a lack of time (i.e. the host shift occurred recently) or due to relatively high gene flow preventing much differentiation at loci not experiencing selection.

Host race formation in the leaf-mining moth Acrocercops transecta (Lepidoptera: Gracillariidae)

“…Shaw, 2002) or from more rapid evolution than nuclear genes (for a review Ballard & Rand, 2005). However, as mtDNA is inherited maternally, mitochondrial gene phylogeny directly reflects the evolutionary history of female host preference, and is useful for estimating the history of host shifts (Diegisser et al ., 2004). The procedures for DNA extracting, PCR, and sequencing were the same as described in Ohshima & Yoshizawa (2006).…”

Complex trait differentiation between host-populations of the pea aphid Acyrthosiphon pisum (Harris): implications for the evolution of ecological specialisation

“…In addition, those traits may either facilitate or impede gene flow between host populations and adaptive evolutionary diversification. Both the level of divergence of such life-history traits between host races and their possible influence on gene flow and reproductive isolation have rarely been investigated; but see also Diegisser et al (2004).…”

Infestation of a novel host plant by Tephritis conura (Diptera: Tephritidae) in northern Britain: host-range expansion or host shift?

“…These phenological differences are reflected in discrete oviposition periods of the associated T. conura host races. Allochronic timing to plant phenologies are observed in all reported tephritid host races (Horner et al 1999;Diegisser et al 2004Diegisser et al , 2006bDambroski and Feder 2007).…”

“…One fragment included portions of the cytochrome oxidase subunit I, tRNA Leu , and portions of the cytochrome oxidase subunit II (referred to as COI/II), the second fragment contained portions of the 16S rRNA, tRNA Leu , and portions of the NADH1 dehydrogenase (16S/ND1). Extraction, amplification and sequencing conditions were identical to Diegisser et al (2004); primers are given in Diegisser et al (2006a).…”

“…The Tephritidae have several well documented host-races, including species in the genera Eurosta (Craig et al 1993), Rhagoletis (Bush 1969;Feder et al 1998) and Tephritis (Diegisser et al 2004(Diegisser et al , 2006a, whereas other studies have either found no or ambiguous evidence for divergent host-plant populations (Leclaire and Brandl 1994;Schwarz et al 2003;Stireman et al 2005;Vaupel et al 2007). Host-range expansions and host shifts likely both explain the range of Cirsium (Cardueae) host plants exploited by the fly Tephritis conura (Tephritidae).…”