Michael F. Braby

The genetic basis of a plant-insect coevolutionary key innovation.

Ehrlich and Raven formally introduced the concept of stepwise coevolution using butterfly and angiosperm interactions in an attempt to account for the impressive biological diversity of these groups. However, many biologists currently envision butterflies evolving 50 to 30 million years (Myr) after the major angiosperm radiation and thus reject coevolutionary origins of butterfly biodiversity. The unresolved central tenet of Ehrlich and Ravens theory is that evolution of plant chemical defenses is followed closely by biochemical adaptation in insect herbivores, and that newly evolved detoxification mechanisms result in adaptive radiation of herbivore lineages. Using one of their original butterfly-host plant systems, the Pieridae, we identify a pierid glucosinolate detoxification mechanism, nitrile-specifier protein (NSP), as a key innovation. Larval NSP activity matches the distribution of glucosinolate in their host plants. Moreover, by using five different temporal estimates, NSP seems to have evolved shortly after the evolution of the host plant group (Brassicales) (≈10 Myr). An adaptive radiation of these glucosinolate-feeding Pierinae followed, resulting in significantly elevated species numbers compared with related clades. Mechanistic understanding in its proper historical context documents more ancient and dynamic plant–insect interactions than previously envisioned. Moreover, these mechanistic insights provide the tools for detailed molecular studies of coevolution from both the plant and insect perspectives.

Synergistic effects of combining morphological and molecular data in resolving the phylogeny of butterflies and skippers

Phylogenetic relationships among major clades of butterflies and skippers have long been controversial, with no general consensus even today. Such lack of resolution is a substantial impediment to using the otherwise well studied butterflies as a model group in biology. Here we report the results of a combined analysis of DNA sequences from three genes and a morphological data matrix for 57 taxa (3258 characters, 1290 parsimony informative) representing all major lineages from the three putative butterfly super-families (Hedyloidea, Hesperioidea and Papilionoidea), plus out-groups representing other ditrysian Lepidoptera families. Recently, the utility of morphological data as a source of phylogenetic evidence has been debated. We present the first well supported phylogenetic hypothesis for the butterflies and skippers based on a total-evidence analysis of both traditional morphological characters and new molecular characters from three gene regions (COI, EF-1α and wingless). All four data partitions show substantial hidden support for the deeper nodes, which emerges only in a combined analysis in which the addition of morphological data plays a crucial role. With the exception of Nymphalidae, the traditionally recognized families are found to be strongly supported monophyletic clades with the following relationships: (Hesperiidae+(Papilionidae+(Pieridae+(Nymphalidae+(Lycaenidae+Riodinidae))))). Nymphalidae is recovered as a monophyletic clade but this clade does not have strong support. Lycaenidae and Riodinidae are sister groups with strong support and we suggest that the latter be given family rank. The position of Pieridae as the sister taxon to nymphalids, lycaenids and riodinids is supported by morphology and the EF-1α data but conflicted by the COI and wingless data. Hedylidae are more likely to be related to butterflies and skippers than geometrid moths and appear to be the sister group to Papilionoidea+Hesperioidea.

When and where did troidine butterflies (Lepidoptera : Papilionidae) evolve? Phylogenetic and biogeographic evidence suggests an origin in remnant Gondwana in the Late Cretaceous

The age, geographic origin and time of major radiation of the butterflies (Hesperioidea + Papilionoidea + Hedyloidea) are largely unknown. The general modern view is that butterflies arose during the Late Jurassic/Cretaceous in the southern hemisphere (southern Pangea/Gondwana before continental breakup), but this is not universally accepted, and is a best guess based largely on circumstantial evidence. The extreme paucity of fossils and lack of modern, higher-level phylogenies of extant monophyletic groups have been major impediments towards determining reliable estimates of either their age or geographic origin. Here we present a phylogenetic and historical biogeographic analysis of a higher butterfly taxon, the swallowtail tribe Troidini. We analysed molecular data for three protein-encoding genes, mitochondrial ND5 and COI–COII, and nuclear EF–1α, both separately and in combination using maximum parsimony (with and without character weighting and transition/transversion weighting), maximum likelihood and Bayesian methods. Our sample included representatives of all 10 genera of Troidini and distant ingroup taxa (Baroniinae, Parnassiinae, Graphiini, Papilionini), with Pieridae as outgroup. Analysis of the combined dataset (4326 bp; 1012 parsimony informative characters) recovered the Troidini as a well supported monophyletic group and the monophyly of its two subtribes, Battina and Troidina. The most parsimonious biogeographic hypothesis suggests a southern origin of the tribe in remnant Gondwana (Madagascar–Greater India–Australia–Antarctica–South America) sometime after the rifting and final separation of Africa in the Late Cretaceous (<90 Mya). Although an ancient vicariance pattern is proposed, at least four relatively recent dispersal/extinction events are needed to reconcile anomalies in distribution, most of which can be explained by geological and climatic events in South-east Asia and Australia during the late Tertiary. Application of a molecular clock based on a rate smoothing programme to estimate various divergence times based on vicariance events, revealed two peculiarities in our biogeographic vicariance model that do not strictly accord with current understanding of the temporal breakup of Gondwana: (1) the troidine fauna of Greater India did not become isolated from Gondwana (Antarctica) until the end of the Cretaceous (c. 65 Mya), well after Madagascar separated from Greater India (84 Mya); and (2) the faunas of Greater India, Australia and South America diverged simultaneously, also at the K/T boundary. A recent published estimate of the time (31 Mya) of divergence between Cressida Swainson (Australia) and Euryades Felder & Felder (South America) is shown to be in error.

Evolution of larval host plant associations and adaptive radiation in pierid butterflies

Butterflies in the family Pieridae (Lepidoptera: Papilionoidea) feed as larvae on plants belonging primarily to three distantly related angiosperm orders: Fabales (legumes and allied plants), Brassicales (crucifers and related plants containing mustard oil glucosides), and Santalales (‘mistletoes’). However, some utilize plants from 13 other families in a further eight orders. We investigated the evolutionary history of host plant use of the Pieridae in the context of a recent phylogenetic hypothesis of the family, using simple character optimization. Although there is a close association between host plant and butterfly higher classification, we find no evidence for cospeciation but a pattern of repeated colonization and specialization. The ancestral host of the family appears to be Fabaceae or Fabales, with multiple independent shifts to other orders, including three to Santalales. The shift to Brassicales, which contain secondary compounds (glucosinolates), promoted diversification and adaptive radiation within the subfamily Pierinae. Subsequent shifts from crucifers to mistletoes (aerial‐stem hemiparasites) facilitated further diversification, and more recent shifts from mistletoes to mistletoe host trees led to exploitation of novel host plants outside the conventional three orders. Possible mechanisms underlying these host shifts are briefly discussed. In the Pierinae, a striking association between host plant, larval and adult behaviour, adult phenotype, and mimicry calls for further research into possible relationships between host specialization, plant chemistry and butterfly palatability.

Systematics, biogeography and diversification of the Indo‐Australian genus Delias Hübner (Lepidoptera: Pieridae): phylogenetic evidence supports an ‘out‐of‐Australia’ origin

Abstract Two alternative hypotheses for the origin of butterflies in the Australian Region, that elements dispersed relatively recently from the Oriental Region into Australia (northern dispersal hypothesis) or descended from ancient stocks in Gondwana (southern vicariance hypothesis), were tested using methods of cladistic vicariance biogeography for the Delias group, a diverse and widespread clade in the Indo‐Australian Region. A phylogenetic hypothesis of the twenty‐four species‐groups recognized currently in Delias and its sister genus Leuciacria is inferred from molecular characters generated from the nuclear gene elongation factor‐1 alpha (EF‐1α) and the mitochondrial genes cytochrome oxidase subunits I and II (COI/COII) and NADH dehydrogenase 5 (ND5). Phylogenetic analyses based on maximum parsimony, maximum likelihood and Bayesian inference of the combined dataset (3888 bp, 1014 parsimony informative characters) confirmed the monophyly of Delias and recovered eight major lineages within the genus, informally designated the singhapura, belladonna, hyparete, chrysomelaena, eichhorni, cuningputi, belisama and nigrina clades. Species‐group relationships within these clades are, in general, concordant with current systematic arrangements based on morphology. The major discrepancies concern the placement of the aganippe, belisama and chrysomelaena groups, as well as several species‐groups endemic to mainland New Guinea. Two species (D. harpalyce (Donovan), D. messalina Arora) of uncertain group status are currently misplaced based on strong evidence of paraphyly, and are accordingly transferred to the nigrina and kummeri groups, respectively. Based on this phylogeny, a revised systematic classification is presented at the species‐group level. An historical biogeographical analysis of the Delias group revealed that the most parsimonious reconstruction is an origin in the Australian Region, with at least seven dispersal events across Wallacea to the Oriental Region. The eight major clades of Delias appear to have diverged rapidly following complete separation of the Australian plate from Gondwana and its collision with the Asian plate in the late Oligocene. Further diversification and dispersal of Delias in the Miocene–Pliocene are associated with major geological and climatic changes that occurred in Australia–New Guinea during the late Tertiary. The ‘out‐of‐Australia’ hypothesis for the Delias group supports an origin of the Aporiina in southern Gondwana (southern vicariance hypothesis), which proposes that the ancestor of Delias + Leuciacria differentiated vicariantly on the Australian plate.

Phylogenetics of Coenonymphina (Nymphalidae: Satyrinae) and the problem of rooting rapid radiations.

We report a rapid radiation of a group of butterflies within the family Nymphalidae and examine some aspects of popular analytical methods in dealing with rapid radiations. We attempted to infer the phylogeny of butterflies belonging to the subtribe Coenonymphina sensu lato using five genes (4398bp) with Maximum Parsimony, Maximum Likelihood and Bayesian analyses. Initial analyses suggested that the group has undergone rapid speciation within Australasia. We further analyzed the dataset with different outgroup combinations the choice of which had a profound effect on relationships within the ingroup. Modelling methods recovered Coenonymphina as a monophyletic group to the exclusion of Zipaetis and Orsotriaena, irrespective of outgroup combination. Maximum Parsimony occasionally returned a polyphyletic Coenonymphina, with Argyronympha grouping with outgroups, but this was strongly dependent on the outgroups used. We analyzed the ingroup without any outgroups and found that the relationships inferred among taxa were different from those inferred when either of the outgroup combinations was used, and this was true for all methods. We also tested whether a hard polytomy is a better hypothesis to explain our dataset, but could not find conclusive evidence. We therefore conclude that the major lineages within Coenonymphina form a near-hard polytomy with regard to each other. The study highlights the importance of testing different outgroups rather than using results from a single outgroup combination of a few taxa, particularly in difficult cases where basal nodes appear to receive low support. We provide a revised classification of Coenonymphina; Zipaetis and Orsotriaena are transferred to the tribe Eritina.

Revised systematics and higher classification of pierid butterflies (Lepidoptera: Pieridae) based on molecular data

The butterfly family Pieridae comprises approximately 1000 described species placed in 85 genera, but the higher classification has not yet been settled. We used molecular data from eight gene regions (one mitochondrial and seven nuclear protein‐coding genes) comprising a total of ~6700 bp from 96 taxa to infer a well‐supported phylogenetic hypothesis for the family. Based on this hypothesis, we revise the higher classification for all pierid genera. We resurrect the tribe Teracolini stat. rev. in the subfamily Pierinae to include the genera Teracolus, Pinacopteryx, Gideona, Ixias, Eronia, Colotis and most likely Calopieris. We transfer Hebomoia to the tribe Anthocharidini and assign the previously unplaced genera Belenois and Dixeia to the subtribe Aporiina. Three lineages near the base of Pierinae (Leptosia, Elodina and Nepheronia + Pareronia) remain unplaced. For each of these, we describe and delineate new tribes: Elodinini Braby tribus nova, Leptosiaini Braby tribus nova and Nepheroniini Braby tribus nova. The proposed higher classification is based on well‐supported monophyletic groups and is likely to remain stable even with the addition of more data.

Biogeography of butterflies in the Australian monsoon tropics

The biogeography of butterflies within the monsoon tropical biome of northern Australia is reviewed in terms of patterns of species richness, endemism and area relationships. Available data indicate that the region supports a relatively rich fauna, comprising 265 species (~62% of the total Australian fauna), but endemism is low (6%). No genera are endemic to the monsoon tropics, but two (Neohesperilla, Nesolycaena) are characteristic components, embracing a total of seven species in the region, of which five are endemic. Three ecological specialists (Neohesperilla senta, Elodina walkeri, Candalides delospila), each associated with different vegetation types, appear to be characteristic elements of the monsoon tropics. Of 67 range-restricted species in the monsoon tropics, 15 (mostly associated with savanna) are endemic to the region, while 52 (mostly associated with rainforest) are non-endemic, occurring also in south-east Asia and/or mainland New Guinea. A pronounced attenuation in species richness from Cape York Peninsula across the Top End to the Kimberley is evident. Within the monsoon tropics, Cape York Peninsula stands out as an area of exceptional biodiversity, with 95% of the butterflies (251 species; 7 endemic species, 31 endemic subspecies/geographical forms) recorded from the entire region, compared with the Top End (123 species; 3 endemic species, 17 endemic subspecies/geographical forms). In contrast, the Kimberley has a comparatively depauperate fauna (85 species; 1 endemic species, 0 endemic subspecies) without strong Indonesian affinities, and contains only two range-restricted species. A sister-area relationship between Cape York Peninsula and the Top End–Kimberley is evident in one clade, Acrodipsas hirtipes (northern Cape York Peninsula) + A. decima (Top End), with a pairwise divergence of ~1% based on mtDNA, and is suspected in another, Nesolycaena medicea (southern Cape York Peninsula) and N. urumelia (Top End) + N. caesia (Kimberley); a further five species show similar sister-area relationships across the Carpentarian Gap but at the level of subspecies or geographical form. Three general and complementary hypotheses are proposed to explain patterns of geographical differentiation of butterflies in the monsoon tropics: (1) the Carpentarian Gap is a biogeographical filter, functioning as a barrier for some species but as a bridge for others; (2) divergence among taxa between Cape York Peninsula and the Top End–Kimberley has occurred fairly recently (Quaternary), probably through vicariance; and (3) the Bonaparte Gap, with the exception of Nesolycaena, is not a vicariant barrier for butterflies in the Top End and Kimberley.

The immature stages, larval food plants and biology of Neotropical mistletoe butterflies (Lepidoptera: Pieridae). II. The Catasticta group (Pierini: Aporiina).

We present an overview of the morphology, larval food plants and general biology of the immature stages of the “Catasticta group”, one of three clades of aporiine pierids that specialize predominantly on mistletoes, based on extensive field observations and captive reared material in Costa Rica, review of the literature, and examination of material preserved in museum collections. Of the 8 genera recognized in the group, 6 are restricted to the Neotropics of which detailed descriptions and/or illustrations are given for 11 species representing the genera Melete, Pereute, Leodonta and Catasticta. The life histories of these taxa are compared with those of Neophasia and Eucheira, two Nearctic genera in the Catasticta group that specialize on host trees of mistletoes. Larval food plants of the Neotropical genera include Struthanthus, Tripodanthus (Loranthaceae), Antidaphne (Santalaceae), Dendrophthora and Phoradendron (Viscaceae), all aerial-stem hemiparasites in the order Santalales. The butterflies are multivoltine and, with the exception of Melete in which adults are possibly migratory, appear to breed throughout the year. Eggs are deposited in clusters on the larval food plant, larvae feed gregariously and spin considerable quantities of silk, particularly in the late instars, adults are frequently aposematic, and at least four genera form complex mimicry rings. In Melete, Pereute, Leodonta and one species of Catasticta, larval instars III–V feed nocturnally and aggregate near the base of the host tree during the day: silken trails are constructed between mistletoe foraging sites and host tree diurnal resting sites to facilitate movement and communication. The morphology and biology of the immature stages of the Catasticta group are compared with other members of the Aporiina, particularly those of Delias, Aporia and the more distantly related Mylothris, and comments made on their systematic relationships. Simple optimization of several key life history traits in the context of a recent phylogenetic hypothesis of the Aporiina suggests aposematism (larval repellent defence and adult warning colouration) evolved once in the common ancestor of the subtribe, but egg clustering and larval gregariousness are derived traits that coincided with the evolution of mistletoe feeding. It is hypothesized that following the evolution of aposematism, the spatial distribution (patchiness) of mistletoe food plants, which are assumed to contain toxic alkaloids, has been a selective force in the evolution of larval gregariousness in these butterflies. Se presentan aspectos generales de la morfología, las plantas hospederas y la biología general de los estadios inmaduros del “grupo Catasticta”, uno de los tres grupos de piéridos del Aporiina que se especializan en matapalos; basándose en observaciones extensas en el campo, crianza en cautiverio en Costa Rica, revisión de la literatura disponible, y el examen de materiales almacenados en colecciones de museos. De los ocho géneros reconocidos en el grupo, se restringen seis al neotrópico; de los cuales se dan descripciones e ilustraciones detalladas para diez especies que representan los géneros: Melete, Pereute, Leodonta y Catasticta. Se comparan las historias naturales de dichas especies con las de Neophasia y Eucheira, dos géneros de neárctica en el grupo Catasticta que se especializan en los árboles hospederos de matapalos. Las plantas hospederas de los géneros de neotrópico incluyen Struthanthus, Tripodanthus (Loranthaceae), Antidaphne (Santalaceae), Dendrophthora y Phoradendron (Viscaceae), todas son hemiparásitos de tallos aéreos y son del orden Santalales. Las mariposas son multivoltinas que se reproducen a través del año, con la excepción de Melete en que los adultos son posiblemente migratorios. Depositan los huevos en grupos en las plantas hospederas; las larvas son gregarias y se alimentan en grupo, y producen cantidades considerables de seda, particularmente en los últimos estadios. Los adultos frecuentemente son aposemáticos, y por lo menos cuatro géneros forman anillos de mimetismo complejo. En Melete, Pereute, Leodonta y una especie de Catasticta, las larvas en III a V se alimentan durante la noche, y durante el día se agregan en las bases de los árboles hospederos de matapalos alimenticios; construyen senderos de seda entre los matapalos en que forrajean y los sitios de descanso del día para facilitar el movimiento y la comunicación. Se comparan la morfología y biología de los estadios inmaduros del grupo Catasticta con otros miembros del Aporiina, particularmente con los de Delias, Aporia y de Mylothris que están menos relacionados, y se presentan comentarios sobre sus relaciones sistemáticas. El mejoramiento de algunos rasgos importantes de la historia natural en el contexto de una hipótesis reciente de la filogenética del Aporiina sugiere que el aposematismo (defensa larval para repeler y la coloración de advertencia de adulto) evolucionó una vez en el ancestro común de la subtribu, pero los huevos puestos en grupos y las larvas gregarias son rasgos derivados que coincidieron con la evolución de alimentarse de matapalos. Se supone que siguiendo la evolución del aposematismo, la distribución espacial (dispersión) de los matapalos, los cuales se considera que contienen alcaloides tóxicos, ha sido una fuerza selectiva en la evolución del gregarismo en su estadio larval, de estas mariposas diurnas.

Life history strategies and habitat templets of tropical butterflies in North-eastern Australia

Three multivoltine species of satyrine butterflies in the genus Mycalesis (Lepidoptera: Nymphalidae) are narrowly sympatric in the wet–dry tropics of north-eastern Australia. They show a range of ecological strategies and adaptations associated with contrasting habitats and varying selective pressures. Two abiotic factors, namely favorability (the reciprocal of seasonal adversity) and predictability (broadly the reciprocal of disturbance), were examined as potential environmental selective forces in shaping their life histories. Comparison of several key life history traits of the ‘wet-season form’ revealed that the life histories of each species corresponded well with their habitat characteristics. M. perseus, which lives in habitats which are less favorable (i.e. adverse) and more unpredictable (i.e. temporary), shows many traits of an r-type strategy: smaller size, faster development, earlier maturation, higher fecundity, smaller egg size, and rapid population increase. By contrast, M. sirius and M. terminus, which live in more favorable and predictable (i.e. permanent) habitats, have many life history attributes and other characteristics in common which link them closer to K-type strategies. The only discrepancy is lower potential reproductive effort of M. perseus, which may be accounted for in terms of an evolutionary trade-off, such as with dispersal or dormancy. Other correlates associated with the M. perseus life history tactic include higher sex-size dimorphism, greater dispersal ability, better tolerance to adverse conditions, stronger phenotypic variation, greater degree of polyandry, and a more flexible breeding strategy. The life history patterns of these species are discussed in the context of evolutionary life history models, particularly the Southwood–Greenslade habitat templet.