The evolution of chemical defences and mating systems in tiger moths (Lepidoptera: Arctiidae)

Abstract

The origin and evolution of allelochemical sequestration in tiger moths (Arctiidae) is a complex interplay of larval and adult strategies and phylogenetic history. Using a phylogeny of Arctiidae, we examine the acquisition of secondary compounds from larval host plants and the use of secondary compounds and ultrasound in male courtship displays. We note that two sets of defensive signals (secondary chemicals and ultrasound) have been incorporated independently into arctiid courtship displays. Pyrrolizidine alkaloids are used in larval defence, and transformed into male courtship pheromones in several lineages. Phylogenetic inertia best explains the presence of adult collection and use of PAS in the absence of larval sequestration. Ultrasound, an adult defensive display directed at bats and other predators, has also been incorporated into arctiid mating displays. Sensory exploitation appears to underlie this co-option of defence signals for mating purposes.

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

“…While not generally recognized as a mate-searching strategy, the ability of males to find plants is well known in other contexts among Lepidoptera. For example, males of certain butterflies and moths harvest alkaloids from withered plant tissue to use as defences and precursors for pheromones (Pliske et al 1976;Weller et al 1999), respond to female sex pheromones more effectively in the presence of plant volatiles (Emelianov et al 2001;Deng et al 2004;Yang et al 2004), or choose nectar sources using visual and chemical floral cues (Weiss 1997;Andersson & Dobson 2003;Cunningham et al 2006). Plants release a wide range of organic volatiles as a result of their interaction with herbivores (Pare & Tumlinson 1999).…”

“…Such colorations probably function to advertise larval toxicity to predators, and, although few cases of mimetic convergence have been proposed, they could also provide species-specific information to searching males (Brown & Benson 1977). Signals that have evolved in a defence context are often also used in intraspecihc signalling (Summers et al 1999;Weller et al 1999;Jiggins et al 2001). For example, females of the pipevine swallowtail butterfly, cued by conspecific larval warning colorations, avoid oviposition on occupied plants, which probably reduces competition for their offspring (Papaj & Newsom 2005).…”

Niche-specific cognitive strategies: object memory interferes with spatial memory in the predatory bat, Myotis nattereri

“…Quinine is a bitter-tasting, odourless alkaloid similar to those sequestered from host plants by some Lepidoptera as caterpillars (Nishida, 2002;Weller et al, 1999) and avoided by the vespertilionid bat E. fuscus . Trials commenced 1-2 h after lights off and a day's trials were completed when the bat had taken (i.e.…”

Fungi Feeding by the Agreeable Tiger Moth (Spilosoma congruaWalker) (Erebidae: Arctiinae)

“…Many sequestered compounds have been identified in arctiines (Hristov & Conner 2005;Wagner 2009), including Spilosoma congrua caterpillars which are highly effective at sequestering iridoid glycosides (Conner 2009;Hristov & Conner 2005). Other arctiines are known to sequester pyrrolizidine alkaloids (Woolley 2001), azoxyglycosides, lichen phenolics, biogenic amines, iridoid glycosides, pyrrolizidine glycosides and cardiac glycosides (Nishida 2002;Weller et al 1999;Bowers 2009) A variety of bioactive secondary metabolites are widely produced by fungi (Zjawiony 2004;Mahmood 2010;Kukor & Martin 1987) and although there are few reports that insects sequester fungal toxins (Wicklow 1988), sequestration of fungal secondary compounds from lichens was shown in 24 lichen feeding lithosiines (Hesbacher et al 1995). The purpose of this note is to document mycophagy in a primarily phytophagous arctiine, Spilosoma congrua Walker.…”