BioRisk 5: | 4 [i= | 53 (20 | 0) Apeer-reviewed open-access journal doi: 10.3897/biorisk.5.855 RESEARCH ARTICLE & B | O R IS k http://biorisk-journal.com/ When south goes north: Mediterranean dragonflies (Odonata) conquer Flanders (North-Belgium) Geert De Knijf, Anny Anselin Research Institute for Nature and Forest (INBO), Kliniekstraat 25, B-1070 Brussels Belgium Corresponding authors: Geert De Knijf (geert.deknijf@inbo.be), Anny Anselin (anny.anselin@inbo.be) Academic editor: /iirgen Ort | Received 20 August 2010 | Accepted 10 September 2010 | Published 30 December 2010 Citation: De Knijf G, Anselin A (2010) When south goes north: Mediterranean dragonflies (Odonata) conquer Flanders (North-Belgium). In: Ott J (Ed) (2010) Monitoring Climatic Change With Dragonflies. BioRisk 5: 141-153. doi: 10.3897/biorisk.5.855 Abstract Since 1980, eight southern dragonfly species have been regularly recorded in Flanders. They show a sig- nificant increase in relative abundance, relative area as well as indications of reproduction since the begin- ning of the nineties, with peak occurrence mainly in the 1995-1999 period. Since 2000, numbers are lower but more species were simultaneously present. Three species, Lestes barbarus, Crocothemis erythraea and Sympetrum fonscolombii, show a combination of earlier arrival, earlier reproduction with a higher frequency and higher maximum ranges and can be considered as having stable populations in Flanders. All other southern species show in general a later arrival, only one confirmed or probable reproduction and have much lower maximum ranges. Two other species, reaching their northern limit of distribution in Flanders, Erythromma viridulum and E. lindenii have clearly expanded their relative area since the eighties. Their relative abundance also increased although this shows more fluctuations. Keywords Odonata, dragonflies, range extension, Belgium, climate change, relative abundance Introduction Climate change on Earth is causing a growing concern. It is still not fully understood whether this is part of normal global climate fluctuations or mainly the result of hu- man activities. Whatever the cause, it is clear that the rate of warming during the last 30 years has been greater than at any other time during the last 1000 years and atmos- Copyright G. De Knijf,A.Anselin. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 142 Geert De Knijf & Anny Anselin / BioRisk 5: 141-153 (2010) pheric CO2 concentrations have never been so high (IPCC 2001). Increasing concern over the implications of this “global warming” for biodiversity have resulted in a large amount of studies on a wide array of taxa, communities and ecosystems (Parmesan and Yohe 2003). Ecological responses are already clearly visible on different levels, although in many regions there is an asymmetry in the warming and in the precipita- tion regimes that undoubtedly will contribute to heterogeneity in ecological dynamics across the system (Hughes 2000; Pefuelas et al. 2002; Walther et al. 2002). As a result of the predicted future increase in global temperatures, between 1.4 and 5.8°C (IPCC 2001; Stainforth et al. 2005), a number of species are expected to shift their ranges in response, rather than adapt to warmer temperatures in situ (Huntley 1991). Among insects, some European butterflies have shifted or expanded their ranges northwards (Parmesan et al. 1999). It is expected that other winged insect species will show similar responses to climate change. However, few studies have focussed on other groups of insects. In particular, there is not much information available on taxa with aquatic larval stages such as dragonflies, and data are often lacking or conflicting (Hickling et al. 2005). In Flanders (Northern Belgium) the distribution and abundance of dragonflies is well known over a long time (De Knijf et al. 2006). Flanders is situated in North- west-Europe, somewhat halfway between the Mediterranean region and Fennoscandia. Moreover, it lays in the smallest part of the (Central) transition zone between the so-called Northern and Southern climatic zones, determined by the 18°C mean July temperature and the 2500 degree day (www.worldclimate.com). ‘Therefore, it seems an interesting region to check for changes in fauna composition which could be due to increasing temperatures. Like most insects, dragonflies have short life cycles and often a high reproduction rate and dispersal capacity. They have the ability to react relatively quickly to changes in climate. The aim of this contribution is to analyse in general to what extend southern drag- onfly species have expanded their range into Flanders. In another paper (in prepara- tion) we will threat in more detail the relations between these distribution patterns and climatic and other environmental variables. This will allow us comparisons with the recent analysis of Goffart (2006) for the adjacent Walloon region. Material and methods Data sources Data are derived from the Gomphus Dragonflies Working Group’s distribution data- base of Flanders. At the end of 2005 it contained about 55.000 records on 66 species, including historical data going back to the 19 century (Selys 1888). All records up to 2004 were used for the analysis. The Odonata were mapped using Universal Transverse Mercator (UTM) 5x5 km grid squares as units. Special efforts have been made to achieve a good coverage of the territory during the last 15 years. For the more Southern Odonata in Flanders (Belgium) 143 recent records the database includes information on precise locality, date and number of observed individuals and life-cycle stage (larva, exuvium, teneral, male, female, adult-copulation, egg-laying) thus providing indications of reproduction and/or per- manent populations. For reproduction, three categories were considered: confirmed (exuvium, larva or tenerals), probable (tandem or egg-laying) and possible (popula- tion with high number of individuals). For historical records however, population and life-cycle information is often lacking or difficult to interpret, in particular from literature sources. Selection of species For our analysis we selected 10 species which have their main distribution area in the Mediterranean part of Europe (Askew 1988; d’Aguilar and Dommanget 1998) but are actually present in Flanders (De Knijf et al. 2006). We distinguished two groups: — group A: 8 species for which Flanders is no part of their historical distribution area (< 1980): Lestes barbarus (Lb), Aeshna affinis (Aa), Anax parthenope (Ap), Or- thetrum brunneum (Ob), Crocothemis erythraea (Ce), Sympetrum fonscolombii (Sf) and S. meridionale (Sm), and Coenagrion scitulum (Cs) although the status of the latter is less clear-cut than for the other 7 species due to its much more fragmented southern distribution range and the probability of its historical distribution area having reached Flanders. — group B: 2 species that reach in Flanders the northern limit of their distribution range: Erythromma lindenii (El) and E. viridulum (Ev). Analysis To detect general changes in range and numbers, we used Relative Area and Relative Abundance in time per Group (combined), and per species. We define Relative Area in a period as the percentage of different 5x5 km UTM squares occupied by the selected species (or by a group) compared to the total number of different squares occupied by all dragonfly species in that period. A higher percentage does not a priori mean a great- er “range” (enlargement of occupied territory) as squares can be clustered without real- ly “enlarging” the range. However, an analysis of the distribution maps per species for the different periods (years) showed that higher relative percentages resulted in a real increase of occupied territory. Therefore, we decided to use this as a measure for broad changes in range. Relative Abundance is the percentage of the combined record num- bers of a group or species compared to the total number of records. We compared first the data for 8 time periods. To obtain sufficient records, we used two broader categories <1900 and 1900-1949 for the “historical data”. From 1950 on, data were grouped in five decades (and one pentade 2000-2004). To better visualize the recent evolution in the last 25 years (1980-2004), figures are given per year. To determine permanent and 144 Geert De Knijf & Anny Anselin/ BioRisk 5: 141-153 (2010) non-permanent populations, we used reproduction frequencies and categories as well as presence patterns of distribution and abundance during the last 25 years. Results Relative area, relative abundance and reproduction per time period (Table 1) For each species group, relative area and abundance are highly correlated (Spearman- Rank A:0.88, B:0.89, p < 0.05). Before 1900 species of Group A were found in 13.8% of the investigated squares. From 1900 onwards the proportion is much lower but in the 1990ties we see a remarkable increase (27%). In the pentad 2000-2004 the pro- portion reaches even 34.6%. For the species of Group B, proportions increase from the 1980ties but vary in the earlier periods. The relative abundance of Group A and B show a similar pattern as the relative area. Both species of Group B have been present in all but one time period. Group A species have been recorded in each time period but numbers are higher before 1900 and since 1990. Indications of reproduction are also higher since that decade. For Group B, reproduction can not always be confirmed in the older data. Relative area and abundance by groups per year in the recent period (1980-2004) For each species group, relative area and abundance are again highly correlated (Spear- man-Rank A:0.97, B:0.87, p < 0.05). The cumulative relative area for both groups dur- ing the last 25 years (Fig. 1) gives for almost all years a higher percentage for Group B than for Group A, except in 1996 and 2003. Compared to the first 15 years, Group A shows a clear increase in relative distribution during the last decade. ‘There is a promi- nent peak in 1996. Table |. Relative area, relative abundance, number of species and reproduction confirmation for Group A (8 spec.) and Group B (2 spec.) in the 8 time periods (** = confirmed reproduction, * = probable re- production, see also Material & Methods). time period Relative area Relative abundance Number of species Group A | Group B | Group A | Group B | GroupA | Group B 1_|<1900 13,8 17,2 ae 2 | 1900-1949 1,8 8,0 2 2 (1*2) 3 11950-1959 1 1*? 4 11960-1969 3 2(1*+1*?) 5 | 1970-1979 2 le) 6 | 1980-1989 2,4 18,2 4 (1*) 2** 7 |1990-1999 2A 39,9 yA 3,8 Tia) 2" 8 2000-2004 34,6 41,1 2 ao Sarr 3"0) 2 Southern Odonata in Flanders (Belgium) 145 The cumulative relative abundance for both groups (Fig. 2) gives a very similar pattern to the cumulative relative area (see Fig. 1). Relative area and distribution by species per year in the recent period (1980-2004) The relative area and abundance per year for each species of Group A separately shows again a clear increase in presence and number of occupied squares in the last 10 years (Fig. 3, 4). Four species (Coenagrion scitulum, Anax parthenope, Orthetrum brunneum and Sympetrum meridionale) remain at a very low percentage and have an irregular presence pattern. Aeshna affinis has slightly higher numbers but is also frequently ab- sent. Lestes barbarus, Crocothemis erythraea and Sympetrum fonscolombii show a rather stable presence although numbers fluctuate. In Lestes barbarus the area is smaller dur- ing the last five years. All three species have a greater or maximum range in 1996, with Sympetrum fonscolombii showing an extreme peak. In Fig. 4 the recent cumulative distribution of Crocothemis erythraea for four con- secutive time periods (a = < 1990, b = 1990-1994, c = 1995-1999 and d = 2000-— 2004) is given. We also indicate the investigated squares (dotted) for each time period. The species shows since 1990 a real increase in distribution area in Flanders. gg1 2 gg? 998 gag fe 2000 2002 2003 ig 2004 2001 year Figure |. Cumulative relative area per year from 1981-2004 for the 2 species of Group B (left: dotted bars) and the 8 species of Group A (right: barred, checkered and black bars indicating respectively no reproduction, probable and confirmed reproduction of at least one species of the group). Geert De Knijf & Anny Anselin/ BioRisk 5: 141-153 (2010) SS Tt a = Y a je SSS ow PS a SS a oe = ESSE ST a SSS SSE’ AANA ae ae Sees is. ae i i @ SSS DASA Fi, aes a SS iy Y = [| 146 80,00 ZBL : e 2 .° un a Lud om = cq | G6L on to 4 6 ff 3 2 Oo 8 OE Aas Oo g o o o o o o o o & o o im] o o im] = o 5 a a 3 a a o = a “ re o re t m ia = a Figure 2. Cumulative relative abundance (%) per year from 1981-2004 for the 2 species of Group B (left: dotted bars) and the 8 species of Group A (right: barred, checkered and black bars indicating respec- tively no reproduction, probable and confirmed reproduction of at least one species of the group). Orthetrum Sympetrum meridionale. SS BEB i ge Aeshna affinis Ob Sympetrum fonscolombii and Sm Anax parthenope Af = Crocothemis erythraea Sf Cs Figure 3. Relative area for the 8 species of Group A in Flanders during the period from 1980-2004. Lb Lestes barbarus Cs = Coenagrion scitulum Ap brunneum Ce Southern Odonata in Flanders (Belgium) 147 First presence, confirmed reproduction and maximum range Table 2 summarises a number of presence and reproduction data. Three species (Lestes barbarus, Crocothemis erythraea and Sympetrum fonscolombii ) show a combination of earlier arrival, earlier confirmed reproduction with a higher frequency and higher maximum ranges. All others (Coenagrion scitulum, Aeshna affinis, Anax parthenope, Orthetrum brunneum and Sympetrum meridionale) show only one (more recent) con- firmed (or probable) reproduction and have much lower maximum ranges. Discussion In the 19th century, six southern species have been observed in Flanders. However, lit- tle is known about their distribution area and population abundance. In historical ref- erences like Selys (1859, 1888) and Bamps and Claes (1893), comprehensive descrip- tions often lack and there is certainly a bias resulting from heterogeneous sampling, low visiting effort and ‘collectioning’. In the following periods, southern species were very rarely observed. Towards the last decades of the 20th century, this changed. Since 1980, eight southern dragonfly species have been recorded in Flanders. ‘The first in row were Anax parthenope (1983), Lestes barbarus and Sympetrum fonscolombii (1984) and Crocothemis erythraea (1987). They were followed by Aeshna affinis (1991), Orthetrum brunneum (1994), Coenagrion scitulum (1999) and finally S. meridionale (2000). In general the present data of this group shows a clear increase in relative abundance as well as relative area since the beginning of the 1990ties, with “peak” occurrence mainly in the 1995-1999 period. Since 2000, numbers are lower but more species were si- multaneously present. However, not all the members of the group have achieved a similar level of ‘expansion’ succes and permanence. Only three of them can actually be considered as having a “permanent” population: Lestes barbarus, Crocothemis erythraea and Sympetrum fonscolombii. Until 1980, only 6 records of Lestes barbarus are known from Flanders, three of them dating from the hot summer of 1976, without proof of permanent populations. In 1984 and 1985, the species was seen in several locations, and at one site there was a very small “population” present but reproduction could not be confirmed. In 1994 and in particular in 1995 there was an invasion of the species in North West Europe (Monnerat 2002; Parr 2003). Since then, the species maintains permanent populations in Flanders (De Knijf 1994; Stoks 1994; Stoks and De Block 1997). Sympetrum fonscolombii has been recorded 10 times before 1980, and although only isolated or very few individuals have been seen, the species might have reproduced in the past (Selys 1859). In the eighties the species had been observed in two sites, but since the nineties it occurs yearly and has been reproducing. Populations of more then 50 individuals have been sighted. Since a peak in 1996 during an invasion in North Western Europe (Dijkstra and van der Weide 1997; Lempert 1997), S. fonscolombii now is present in several tens of squares and maintains populations on several sites, also in the southern part of Belgium (Goffart 1999; Paternoster 2000). Crocothemis eryth- 148 Geert De Knijf & Anny Anselin/ BioRisk 5: 141-153 (2010) a Da R ra oleae i Bai | 4 F | | jos H oH LH ee eT |_| ( | tt Ro | = pe He f a! en ee nd MOOSE he ia b ~ Pa a | aS Aa Atte tA ae 7 HS - ‘a 1 || | a —_ pal _ | estes cated a1 + 4 |_ ae me Bee t | eo a edi | ( | ae i | i era ‘ al a) aN uy Pe | iy gt he al 7 “Eo Cc | | 4liil\i | | @ PAB d “s | ee Figure 4, Cumulative distribution of Crocothemis erythraea in four consecutive time periods (a =< 1990, b = 1990-1994, c = 1995-1999 and d = 2000-2004) in Flanders, based on 5 x 5 km squares. For each time period the investigated squares are given as dotted squares in the background. Southern Odonata in Flanders (Belgium) 149 Table 2. Presence during the first five time periods (1—5) (see also Tab. 1) and year of first and last record in the period 1980-2004; Recent reproduction: first (Y1) and last year (Y2), time interval between Y1 and Y2 and frequency of reproduction in that period for confirmed** and probable* together; Maximum “range” recent: cumulative number of occupied 5x5 km squares in the period 1980-2004. Lb = Lestes barbarus, Cs = Coenagrion scitulum, Ap = Anax parthenope, Af = Aeshna affinis, Ob = Orthetrum brunneum, Ce = Crocothemis erythraea, Sf = Sympetrum fonscolombii and Sm = Sympetrum meridionale. Lb | Sf | Ce Ob | Cs | Sm Records Non-recent time (period 1-5) | 1,2,5 | 1,3,4| 4 Recent time (period 6-8) first | 1984 | 1984 | 1987 1994 | 1999 Recent time (period 6-8) last | 2004 | 2004 | 2004 | 2003 | 2004 | 2004 | 2004 | 2003 Reproduction recent First: Y1 O94 | T9898 | HO 90%"| 2003%) | 19965" - 2003*%| 20037 1999S |e 9920" Latest: Y2 2004** oe a - 2003* | 2003** Y1 - Y2 S - 1 1 Frequency in Y1 - Y2 - 1 1 Max. “range” recent 115 Ts oo [535 See |e Xe reae is without doubt the most successful of all southern species. The species has been observed in the past (Selys 1878), but permanent populations or reproduction have never been recorded. Apart from observations in 1963 (Cammaerts 1967; Dumont 1967), the species was only seen more regularly since the eighties when first reproduc- tion was proved but is now present in more then 20% of all squares (De Knijf 1989, 1995; Tailly 1991). Anax parthenope has only once been observed in the surroundings of Brussels in 1884 but after this, the species was not recorded anymore until the eight- ies when there are several observations (all males) (Lerner 1984, Michiels 1984). In the nineties however, Anax parthenope has been recorded in 6 localities in Flanders, mostly individual males, with a small invasion in 1999 (De Knijf 1999). Probable reproduc- tion was only recorded in 2003. It is clear that the species has still no permanent popu- lations in Flanders. Aeshna affinis has never been observed in Flanders before 1900 and there is only one record (1969) before 1980. The species was again observed in 1991 and present in almost every year since 1994. An invasion in 1995 with higher numbers probably resulted in the first proof of reproduction in 1996 (Van de Meutter 1995; Andries 1997; Van den Berghe 1999). At several localities the species has been seen in consecutive years, but it cannot yet be considered as having permanent populations in Flanders. From Orthetrum brunneum there exist only a very few historical records although it might have reproduced in the past (Bamps and Claes 1893). Since 1980, the species was first recorded in 1994 (Verstraeten 1996) and has been present regularly but in very small numbers (Van de Meutter 2004). Reproduction occurred probably in 2005. Orthetrum brunneum has to be considered as an irregular and very rare spe- cies in Flanders. Coenagrion scitulum has been mentioned a few times by Selys (1868) but in contrary with the Walloon region without proof of reproduction in Flanders. 150 Geert De Knijf & Anny Anselin/ BioRisk 5: 141-153 (2010) 30 ria 25 ro EEE [1 > ee -, 20 ae oe SSS iy i Se hi by = nm Es Ea ee te ke te te ke te te te ke te te te ke te ke ke ke te ke te te te ke te te te te te ee ba a ta bs ie SS | s FS P ie ba ka ka Ea a Es Es EB ie : is i ss FAG bee a Ea te ie Ee Ee be ie Ea Ee Ea Ey EB Ee i ts EA a B ZY Zh. ZY AY GY Gay & 4 Sas SS Sol LSS Fs p [| mo SS fo C - WwW Ot © Oo Re DBD BB Bf A He Fs BD wo Kr a o - AW t oo 6 Oo 6G Hb oO ho HH HF TF SH HF FH HF HF BD 6S oo 6 o nn nan ae mF oF TF FF HF SH FF SF HF GF SF FHF GF o 8 8 o a a i | ian] year Figure 5. Relative abundance for the 8 species of Group A in Flanders in the period 1980-2004. Lb = Lestes barbarus Cs = Coenagrion scitulum Ap = Anax parthenope Af = Aeshna affinis Ob = Orthetrum brunneum Ce = Crocothemis erythraea Sf = Sympetrum fonscolombii and Sm = Sympetrum meridionale. Later only a few records are known from 1949 and 1973. Since 1980, the species has only been observed in 1998, in 2003 and in 2004, and although most probably there are now some small local populations present where reproduction may occur, the spe- cies can not be considered as permanently established yet (De Knijf 2004). The only known record of Sympetrum meridionale from the past dates from 1886 (Bamps and Claes 1893). In 2000 the species was seen again at two different localities, with even a young male at one site (Versonnen et al. 2002). In 2001 only one female was seen (Versonnen et al. 2002) and in 2002 no records are know. In 2003 reproduction took place at least at one site, with the observation of several tenerals. Since then, the species has not been observed again. ‘Iwo species reaching their northern distribution range in the region, Erythromma viridulum and E. lindenii have permanently maintained it and even expanded their area (see also De Knijf 1995), although there are fluctuations in distribution and abundance. The presented patterns of range extension of the southern species in Flanders are a part of a more general long-term expansion of these species into Northwest Europe (Reder 1993, Drees et al. 1996, Ott 1996, 2000, 2001, Dijkstra and van der Weide 1997; Lempert 1997; Vanderhaeghe 1999; Gonseth and Monnerat 2001; Guerold et al. 2001; Ketelaar 2002; Mauersberger 2003; Parr et al. 2004). However, whether in our region the observed patterns are only (or mostly) a result of increasing tempera- tures as is the case in Wallonia (Goffart 2006), or whether other environmental vari- ables play also an important role, has still to be confirmed. This will be investigated in the next future. 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