Geographic biotype and host-associated local adaptation in a polyphagous species, <I>Lambdina fiscellaria</I> (Lepidoptera: Geometridae) feeding on balsam fir on Anticosti Island, Canada

Abstract

The debate about mechanisms underlying the evolution of host specialization by herbivorous insects remains open. Natural selection may act locally and lead to different patterns of geographic variation in life history traits of polyphagous herbivores. The hypothesis of genetically-based trade-offs in offspring performance on different hosts has been proposed but this has rarely been demonstrated. Under laboratory conditions, the biological performance of two populations of the hemlock looper Lambdina fiscellaria (Guenée), a highly polyphagous lepidopteran, was compared when reared on three different tree host species: balsam fir, eastern hemlock and sugar maple. One population originated from Anticosti Island, Québec, Canada, where the insect has evolved without having access to two of the three tree species tested, the other being from the mainland where all tree species are present. When reared on balsam fir foliage, which was naturally available to each population, larvae from Anticosti Island underwent four instars compared with five for the mainland population, indicating the existence of geographic biotypes in L. fiscellaria. When reared on the foliage of non-naturally available host trees, larvae from Anticosti Island had a higher incidence of supernumerary instars. This is a unique example where local adaptation to environmental conditions of an insect herbivore is expressed through a differential number of larval instars. Moreover, the Anticosti Island population showed a higher growth related index on the host available to both populations indicating that a fitness trade-off was the evolutionary process underlying the local adaptation of this population on balsam fir.

Differential invasion success among biotypes: case of Bemisia tabaci

“…Biotypic variations within species have been extensively described in whiteflies and aphids. Biotypic variation has been related to insecticide resistance (Horowitz et al 2005), host range (Dolatti et al 2005;Hebert et al 2006), plant physiological disorders induced by the insect (Yokomi et al 1990) or differential fitness (Jyoti and Michaud 2005). These differences tend to persist when several biotypes are brought in sympatry, suggesting at least partial reproductive isolation among them; however the exact degree of isolation is usually unknown (Diehl and Bush 1984).…”

Report of a rapid pest risk analysis for Lambdina fiscellaria (Guenée, [1858]) (Lepidoptera: Geometridae) for the island of Ireland

“…Other species of Abies are grown in the PRA area, often for Christmas tree production. Within the laboratory, L. fiscellaria fiscellaria first‐instar larvae have been reared successfully on foliage from a number of hosts that the pest has also been recorded on in the wider environment (Carroll, ; Hérbert et al ., ). Though the pest shows a preference for A. balsamea in its native range, it clearly has some ecological plasticity on host choices.…”

Linking adaptation, delimitation of evolutionarily significant units (ESUs), and gene function: a case study using hemlock looper ecotypes

“…A study of the cytochrome oxidase I and II genes of mitochondrial DNA (mtDNA) for three subspecies of L. fiscellaria [ L.f. fiscellaria , L.f. lugubrosa (Hulst), L.f. somniaria (Hulst)] indicated some genetic polymorphism between subspecies but did not clearly differentiate subspecies (Sperling et al , 1999). Two geographic ecotypes of L.f. fiscellaria are recognized in eastern North America, of which the northern ecotype undergoes four larval instars and the southern ecotype undergoes five larval instars (Hébert et al , 2006; Berthiaume, 2007). Laboratory experiments have confirmed that this trait is fixed through rearing the two ecotypes under the same environmental conditions, in which the ecotypes maintained their respective number of larval instars (Berthiaume, 2007).…”

“…Additional significant differences in life‐history traits include: (i) faster development of the four‐instar ecotype compared to the five‐instar ecotype; and (ii) lower fecundity but greater egg size in the four‐instar ecotype (Berthiaume, 2007). It has been hypothesized that these traits are an adaptation to the latitudinal difference in climate in which these ecotypes reside (Hébert et al , 2006; Berthiaume, 2007). The most serious outbreaks have been reported from the northern parts of the range of the hemlock looper (Martineau, 1984) and are therefore of higher concern from a pest management perspective.…”