Population Genetics of Farmland Sawflies
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Population Genetics of Farmland Sawflies Cook, N.1,2; Karley, A.J. 1; Russell, J.R.1; Parish, D.3; Hubbard, S.F. 1,2 1Environment Plant Interactions, Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA 2Division of Plant Sciences, University of Dundee at SCRI, Invergowrie, Dundee, DD2 5DA 3Game and Wildlife Conservation Trust, 2 East Adamston Farm Cottages, Muirhead, By Dundee, DD2 5QX Figure 1: A Grey Partridge (Perdix perdix) male. A UK Biodiversity Action Plan (BAP) “priority Figure 2: The Yellowhammer (Emberiza citrinella). species”. Also a BAP priority species. sl-CSD: In addition to the haplodiploid Over the last 50 years It has been suggested that a key sex-determining mechanism or so populations of component of the fledgling diet may be the characteristic of all certain farmland bird hymenopteran insects, some larvae of grassland sawflies (Hymenoptera, species have undergone species also possess Symphyta) (Fig. 3), and that intensification single-locus Complementary Sex severe declines. Among the has reduced the numbers of these insects to Determination (sl-CSD). When key indicator species are Grey the extent that they limit the population size of sl-CSD is also present the sex of Partridges (Fig. 1), Yellowhammers an individual is not only bird species that depend on them2. (Fig. 2) and Corn Buntings. The dependant upon ploidy (haploid Sawfly populations may be more than usually susceptible male, diploid female) but on the population declines of these allelic composition at a single to disturbance by farming practices for a number of species are generally attributed to sex determining gene locus. “farming intensification”. One of reasons. Firstly their adult stages are poor dispersers and Hemizygotes (haploid the possible effects of intensive secondly some species are known to possess single locus individuals) develop as normal 3 males. Heterozygotes at the Figure 3: A common farmland Complementary Sex Determination (sl-CSD) . In combination farming prescriptions could be that locus develop as normal diploid sawfly larva. Unknown species. these characteristics might produce an abundance of sterile they affect the supply of insect Symphytan larvae are similar in females but homozygotes at the appearance to the larvae of males as a result of inbreeding and therefore play an locus develop as sterile diploid food to bird populations at critical lepidopterans but distinguished by 1 the presence of 6 or more pairs of important part in the population decline. males. points in their breeding cycle . abdominal pro-legs. Materials & Methods Results If poor dispersal rates and sl-CSD are present in Microsatellite markers for the farmland sawfly populations it should be possible to common British farmland detect their presence through patterns of genetic sawfly species Tenthredopsis variation within and between sawfly populations at a nassata (Fig. 5) and range of spatial scales, and from both intensive and Tenthredopsis excisa are in non-intensive farms. development. Once the markers are fully developed Sawflies are only present in the winged (adult) form we will be able to compare from April to August in Scotland therefore all insects for genetic diversity between study must be obtained during this period. Sawflies are sampling sites and relate this Figure 5 : Tenthredopsis nassata. A common British being collected in grass margin/set-aside land at 3 farmland sawfly. to the environmental factors contrasting farm sites via the use of malaise traps (Fig. prevailing at each site. We 4). Traps are collected from on a weekly basis and the should also be able to trap is then moved to a new random position within its determine the extent to which sampling area for the following week. sawflies are moving around in the farmland habitat. Figure 4: A standard malaise The first indicator that sl-CSD trap. The trap is of a neutral colour and is is present in a field population Figure 6: Chart showing the sex ratios at all six collection sites open-sided. Insects (2009) for T. nassata and the overall sex ratio. are directed upwards is a male-biased sex ratio. For by the shape of the structure into the all sampling sites in 2009 the ethanol-filled ratio of males to females was collection bottle. significantly higher for both T. nassata (Fig. 6) and T.excisa Genetic variation will be quantified by the (Fig. 7). Flow Cytometry will be development of microsatellite markers, and used to definitively confirm the presence/absence of sl-CSD will be References or deny the presence of 1 Chamberlain, et al. (2000). "Changes in the determined by flowcytometric analysis abundance of farmland birds in relation to the timing of sl-CSD in these agricultural intensification in England and Wales." Journal of Figure 7: Chart showing the sex ratios at all six collection sites of neuronal cell DNA content. Applied Ecology 37: 771-788. populations. (2009) for T. excisa and the overall sex ratio. 2 Potts, G. R. (1986). The Partridge. Pesticides, predation and conservation. Collins; London; UK. 3 van Wilgenburg, et al. (2006). "Single locus complementary sex determination in Hymenoptera: an "unintelligent" design?" Frontiers in Zoology 3(1)..