Morphological Diversity of Ground Beetles (Coleoptera: Carabidae) in Scottish Agricultural Land
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J. Zool., Lond. (1999) 247, 1±18 # 1999 The Zoological Society of London Printed in the United Kingdom Morphological diversity of ground beetles (Coleoptera: Carabidae) in Scottish agricultural land I. Ribera1*, D. I. McCracken1, G. N. Foster1, I. S. Downie1 and V. J. Abernethy2 1 Environmental Division, Scottish Agricultural College, Auchincruive, Ayr KA6 5HW, Scotland, U.K. 2 Institute of Biomedical and Life Sciences, Division of Environmental and Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K. (Accepted 25 June 1998) Abstract The morphospace de®ned by 87 species of ground beetle (Coleoptera: Carabidae) of Scottish non-forested habitats is described with multivariate methods, using 13 linear quantitative measurements of the body, hind legs, eyes and antennae, plus ®ve qualitative characters concerned with body shape, colour, wing development, and pubescence. Relationships between pairs of variables are studied with phylogenetic independent contrasts, using two different taxonomic classi®cations as an approximation to the phylogeny of the group. The ®rst ordination axis of the morphospace was found mainly to re¯ect the positive correlation between length of the antennae and length of the hind legs, the second to re¯ect the width of the head, diameter of the eye and pronotum height, and the third the width of the pronotum and elytra, length of the metatrochanter and width of the metafemur. The principal relationships involving qualitative characters were between colour of the body and legs and shape of the pronotum with ordination axes, wing development with width of the elytra, and pubescence with colour of the legs. Most correlations between quantitative variables, in particular those most in¯uencing the ordination axes of the morphospace, remained signi®cant when measured with phylogenetic independent contrasts using both classi®cations. Independent contrasts comparing qualitative with quantitative variables or ordination axes were only signi®cant for the colour of the body with the second axis for both classi®cations used, and length of the antennae with colour of the body and shape of the pronotum for only one of the classi®cations. The main morphological trends within the morphospace de®ned are related with published information on their performance, in particular running speed and pushing abilities, following previous work on the functional morphology of the group. The morphospace de®ned by the species studied is a fundamental tool that will allow further investigations on the relationships between their morphology and life traits, as well as on the relationships of the functional diversity thus characterized with environmental correlates. Key words: Scotland, agriculture, Carabidae, functional morphology, independent contrasts INTRODUCTION fairly uniform in morphology (Thiele, 1977). Although early studies on the morphological adaptations of cara- The Carabidae, with more than 25 000 species on all bids tried to associate morphological characters with major biogeographical regions of the world, is one of habitats (e.g. Sharova, 1974), only a few adaptations to the most diverse families of Coleoptera (Thiele, 1977). special environments have been found, among them Carabid taxonomy and biogeography have been digging, tree-dwelling, or cave-dwelling species. Most thoroughly investigated since the beginning of modern morphological variability within the group is associated entomology, and there is now a wealth of information with differences in habits, especially locomotion and on the basic biology and ecology of ground beetles (see modes of nutrition (Manton, 1977; Evans, 1990). e.g. Thiele, 1977; Desender et al., 1994; LoÈvei & Sunder- Early attempts to describe the functional morphology land, 1996; NiemelaÈ, 1996). of the group did not quantify characters (e.g. Thiele, Despite the taxonomic diversity of the family, ground 1977). Subsequently, more detailed descriptions of the beetles have little variation in basic body structure, being morphological variability associated with specialized modes of feeding, in particular of species preying *Present address: Department of Biology, Imperial College at Silwood on Collembola, were made by Forsythe (1983a, Park, Ascot, Berkshire SL5 7PY, U.K. 1991), Evans & Forsythe (1985), Bauer (1985a,b) and 2 I. Ribera ET AL. Morwinsky & Bauer (1997). Morphological correlates ecological studies (Foote, 1992, 1997; Reilly & Wain- of different modes of locomotion were studied by Evans wright, 1994; Ricklefs & Mails, 1994; Roy & Foote, (1977, 1986), Evans & Forsythe (1984) and Forsythe 1997). In a subsequent paper the relationships between (1981, 1983b, 1987) in an important series of papers. the described morphospace and selected life traits will According to these authors, the ancestral design of be explored (Ribera et al., submitted). Future work will carabids would be an adaptation to running and wedge- study the relationship between functional diversity, as pushing. Possible adaptations to run fast and push de®ned here, and environmental characteristics within forward horizontally superimposed on this basic pattern Scottish agricultural land. were identi®ed, in a trade-off of characters mostly affecting the morphology of the hind legs, in particular the size of the metatrochanters. Trochanters contain the MATERIAL AND METHODS femoral rotator muscle, which is hinged longitudinally to the head of the femur to allow its rotation about the Material trochanter (Evans, 1977). Three main types of locomo- tion were recognized. `Group I' species were considered Specimens were collected during 1995 and 1996 using to be adapted to fast running, and had weak horizontal pitfall traps in different agricultural habitats, ranging pushing abilities. They had short metatrochanters, long from intensive cereal ®elds to upland moorland with and narrow leg segments, and a lightly built body low grazing pressure, in 63 localities around Scotland structure (e.g. the genera Cicindela, Nebria, Leistus, (see Abernethy et al., 1996, for more details on the Notiophilus, Loricera, and Elaphrus). `Group II' species sampling method and information on the localities, with were considered to be adapted to strong wedge-pushing, the exclusion of 3 coniferous forests the species of which with medium speed. They had long metatrochanters, were not included in the present study). Sites were with broad femora, and a variable body shape (e.g. representative of the range of agricultural habitats in Harpalus and Amara). `Group III' species were consid- Scotland, and the species studied constitute the great ered to be adapted to strong horizontal-pushing, and majority of the carabids living in them (as estimated were the slowest species. They had short and narrow with rarefaction methods: Downie et al., 1998). The hind legs, long and pedunculate bodies, and usually British, and in particular the Scottish, fauna of ground front legs with special adaptations for digging (e.g. beetles is clearly impoverished, but constitutes a good Clivina, Scarites,andDyschirius). Carabini (mainly the representation of the wider family. All major taxonomic genus Carabus) had intermediate characteristics, more groups represented in the western Palaearctic fauna are similar to Group II (see Evans, 1986 for a summary of included in the study, which gives a general framework carabid locomotion types and characteristics). Some of in which other species with similar morphologies can be these interpretations were supported by direct measure- easily accommodated. Species with deviating morpholo- ments of the performance of several species in the gies living in particular habitats (e.g. arboricolous laboratory for their running velocity, horizontal species, such as Dromius) were not included in the study, pushing, and wedge pushing (Evans, 1977; Forsythe, to avoid the strong bias they would introduce in the 1981). comparative analysis. Although carabids do not form a Despite the abundant information concerning indivi- community in the ecological sense because of their wide dual sets of characters, no general multivariate analysis range of resource use (LoÈvei & Sunderland, 1996), they of the shape of ground beetles has been conducted in form a well-de®ned evolutionary unit with a similar which the morphological diversity of a representative body plan, and are well suited for the quanti®cation of group of species (the morphospace in the sense of the morphospace they de®ne (e.g. Gould, 1991). Gould, 1991) is described and the main morphological trends identi®ed. In addition, previous work did not take into account the possible biases introduced in the Morphological measurements analysis due to the non-independence of the characters produced by the phylogenetic proximity of the species Thirteen linear quantitative measurements and 5 quali- (Harvey & Pagel, 1991), and in consequence all adaptive tative characters were collected from 87 species interpretations of character correlations must be made occurring in Scottish agricultural land (Tables 1 & 2; with caution. Appendix 1). All species found were included in the The aim of this paper is to describe the morphological analysis with the exception of 8 (making a total catch of space de®ned by species of ground beetles occurring in 95 species), of which very similar species of the same Scottish agricultural land, and to identify character genus or subgenus were already measured. Measure- associations. If such character correlations occur inde- ments were chosen to best characterize