The Seaweed Fly (Diptera: Coelopidae)
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View metadata, citation and similar EEN919papers at core.ac.uk Dispatch: 08.09.07 Journal: EEN brought to you by CORE Journal Name Manuscript No. B Author Received: No. of pages: 6 ME:provided Pradeep by Stirling Online Research Repository 1 Ecological Entomology (2007), 32, 1–6 2 3 4 5 6 7 8 Change in the distribution of a member of the strand 9 line community: the seaweed fl y (Diptera: Coelopidae) 10 11 12 DOMINIC A. E D W A R D 1 , JENNIFER E. BLYTH 2 , RODERICK 13 MCKEE 1 and ANDRÉ SIMON GILBURN 1 1 School of Biological and Environmental Sciences, 14 2 15 University of Stirling, Stirling, Scotland, U.K. and Environmental and Marine Biology, Åbo Akademi University, Turku, Finland 16 17 Abstract . 1. Coastal organisms are predicted to be particularly susceptible to the 18 impact of global warming. In this study the distribution and relative abundance of two 19 coastal invertebrates, Coelopa frigida (Fabricius) and C. pilipes are investigated. 20 21 2. Coelopa pilipes has a more southerly distribution than C. frigida , and prefers a 22 warmer climate. Coelopa pilipes is less resistant to sub-zero temperatures than C. frigida 23 and its northerly distribution is probably limited by cold winter days. 24 3. The most recent distribution map of C. frigida and C. pilipes in northern Europe 25 was published a decade ago and showed the northerly extent of the distribution of 26 C. pilipes reaching the north coast of mainland Scotland but its complete absence from 27 the Western and Northern Isles. 28 4. C. pilipes has now spread throughout the Western Isles and the Orkney Islands but 29 is still absent from Shetland. There has also been an increase in the relative frequency of 30 C. pilipes at sites harbouring coelopids on the British mainland. A similar pattern of 31 distribution change along the west coast of Sweden is reported. 32 33 5. It is proposed that these changes have occurred primarily as a result of global 34 warming and in particular due to the recent increase in winter temperatures. A number 35 of other indirect effects may have also contributed to these changes, including a probable 36 change in macroalgae distribution. The implications of these changes for the wrack bed 37 ecosystem and at higher trophic levels are considered. 38 39 Key words . Climate change , Coelopidae , competition , distribution change , global 40 warming , seaweed fl y . 41 42 43 Introduction Hughes, 2000 ). Poleward range shifts have since attracted em- 44 pirical support on a global scale ( Walther et al. , 2002; Parmesan 45 Global temperatures have increased by approximately 0.6 °C & Yohe, 2003; Hickling et al. , 2005, 2006 ; Mieszkowska et al. , 46 over the past century ( Jones et al. , 1999; IPCC, 2001 ). In Central 2006 ) and models show that these changes can be associated 47 England, the 1990s were approximately 0.5 °C warmer than the with a changing climate ( Walther et al. , 2005 ). 48 1961 – 1990 average; with the greatest increase in temperature Coastal organisms may be particularly susceptible to the im- 49 being experienced during the winter months ( Hulme et al. , pacts of global warming resulting from increases in both sea 50 2002; Watkinson et al. , 2004 ). It is now increasingly apparent temperature and rising sea levels ( Lawrence & Soame, 2004; 51 that climatic change will not only contribute to ecological Watkinson et al. , 2004 ). Correspondingly, a number of intertidal 52 changes in the future, but that change is occurring in the present organisms found on rocky shores around Britain have under- 53 ( Hughes, 2000; Root et al. , 2003 ). One widely predicted out- gone poleward range shifts associated with climate change 54 come is that the ranges of many species will shift either pole- ( Mieszkowska et al. , 2006 ). Among the organisms most likely 55 ward or to higher altitudes ( Barry et al. , 1995; Parmesan, 1996; to be affected are the coastal invertebrates ( Beukema et al. , 56 2001; Lawrence & Soame, 2004; Kendall et al. , 2004 ). Changes 57 to coastal invertebrate communities may be expected to have a 58 Correspondence: Andre Gilburn, School of Biological and Environ- subsequent effect upon other species, particularly avifauna, that 59 mental Sciences, University of Stirling, Stirling, Scotland FK9 4LA, depend upon them as a food source ( Kendall et al. , 2004; 60 U.K. E-mail: [email protected] Lawrence & Soame, 2004 ). 61 62 © 2007 The Authors 63 Journal compilation © 2007 The Royal Entomological Society 1 1 2 Dominic A. Edward et al. 2 3 One particularly understudied coastal ecosystem is the strand temperatures. In addition, the larvae of C. frigida are found to 4 line community ( Kendall et al. , 2004 ), which is founded prima- prefer cooler microhabitats within wrack beds ( Phillips et al. , 5 rily upon marine macroalgae deposited on beaches by storms 1995b ). Data on the relative abundance of northern European 6 and tides. Seaweed flies (Diptera: Coelopidae) inhabit deep al- populations of Coelopids going back nearly 40 years provide an 7 gal deposits, known as wrack beds, deposited on the strand line excellent opportunity to consider the impacts of climate change 8 close to rocky shores ( Dobson, 1974 ). Coelopid larvae are en- upon the strand line community. The aim of this study is there- 9 tirely dependent upon algae for their development and adults fore to assess the relative responses of C. frigida and C. pilipes 10 mate and feed within deposits, using them as places of shelter. to climate change. 11 Both the larval and adult life stages play an important functional 12 role; accelerating decomposition and recycling of nutrients 13 ( Harrison, 1977; Robertson & Mann, 1980; Koop & Griffiths, Materials and methods 14 1982; Cullen et al. , 1987 ) and providing a food source for 15 coastal bird species ( Feare & Summers, 1985 ). Experimental procedure 16 The relative distribution and abundance of two northern 17 European coelopids, Coelopa frigida (Fabricius) and Coelopa Historical data were collated from previous collections 1 18 pilipes (Halliday), has been studied on a number of previous made between February 1967 and October 1990 ( Butlin, 19 occasions ( Egglishaw, 1960; Dobson, 1974; Butlin, 1983; 1983; Gilburn, 1992 ; Phillips et al., 1995; Day & Gilburn, 20 Phillips et al. , 1995b ; see Fig. 1 ). Coelopa frigida occupies unpubl. data). The same areas as for the historical collections 21 higher latitudes ranging from the north coast of France as far were re-sampled between August 2004 and December 2005, 22 north as Iceland and Spitzbergen. In contrast, the range of returning to the same beach and at the same time of year 23 C. pilipes extends farther south down the Atlantic coastline of where possible. If no wrack bed could be found at a site then 24 France yet north only so far as the northern coast of the we located and sampled from the nearest wrack bed to the 25 Scottish mainland. C. pilipes is notably absent from the original site. In some regions no information was available on 26 Western and Northern Isles of Scotland. While both species the exact location of past collections, for example Norway 27 occur sympatrically throughout much of their range, within and the Scottish Islands. In these cases, a number of sampling 28 British wrack beds C. frigida has been described as the most sites were identified to give a comprehensive description of 29 abundant of the large Diptera ( Egglishaw, 1960 ). On mainland coelopid populations. 30 Europe C. pilipes has been recorded as far north as the west The same two collection techniques were adopted as used to 31 coast of Sweden though only very rarely at greater abundances collect the historical data. If sufficient adult flies were present 32 than C. frigida . at a site then they were collected by mouth pooter and trans- 33 While various factors may play a part in determining the ported back to Stirling, where the relative abundance of the two 34 relative abundances of C. frigida and C. pilipes the most impor- species was calculated. At sites lacking large numbers of adults, 35 tant is almost certainly temperature ( Phillips et al. , 1995b ). This collections of larvae were made from various locations and 36 is reflected in a greater abundance of C. pilipes during the sum- depths within the wrack bed and placed in large plastic tanks. 37 mer months ( Remmert, 1965; Phillips et al. , 1995b ) and a Larvae were transported back to Stirling and allowed to de- 38 greater susceptibility of this species to the effects of freezing velop within the seaweed in which they were collected. Any 39 40 41 42 43 44 45 46 47 48 49 50 51 52 Fig. 1. Distribution maps of C. frigida and 53 C. pilipes , past and present. The map on the 16 54 left shows the historical distribution, adapted 55 from Phillips et al. (1995b) , while on the right data from the current study are shown. 56 Filled circles represent populations of 57 C. frigida ( C. pilipes rare if present), empty 58 circles populations of C. pilipes ( C. frigida 59 rare if present) and half fi lled circles mixed 60 populations. 61 62 © 2007 The Authors 63 Journal compilation © 2007 The Royal Entomological Society, Ecological Entomology, 32, 1–6 1 Change in seaweed fl y distribution 3 2 3 collections at high larval density were given additional seaweed was not found to affect the proportion of C. pilipes within = = 4 to reduce the effects of larval competition. The relative number British mainland populations ( F1,66 0.06, P NS). 5 of C. frigida and C. pilipes adults eclosing from these cages 6 was then determined. 7 Scottish Island populations of Coelopids 8 9 Statistical analysis Phillips et al.