Effects of Climatic Changes on Odonata: Are the Impacts Likely to Be the Same in the Northern and Southern Hemispheres? JÜRGEN OTT & MICHAEL J
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Effects of Climatic Changes on Odonata: Are the Impacts likely to be the Same in the Northern and Southern Hemispheres? JÜRGEN OTT & MICHAEL J. SAMWAYS The effects of climatic changes are dif- for the northern hemisphere, where the reasons for this is that in this There is, however, very good evidence ferent in the northern and southern studies are available e.g. for Europe, region, there have been many climatic that certain species are confined to cli- hemispheres – but to date, no formal United States and Japan (Ott 2001, sub- bottlenecks as well as climatic cycling, matic refugia, when formerly they were comparison has been carried out to mitted). In Europe, some Mediterranean including El Niño events. It seems that likely to be more widespread. Today, determine whether climate change has species have expanded their ranges many of the savanna species at least for example, Chlorolestes fasciatus con- comparable effects on the distribution within the last two to three decades over are highly opportunistic and habitat- fined to the Mountain Zebra Park (as patterns and the ecology of dragonfly as much as several hundreds of kilome- tolerant, moving readily in response to well as other mountain ranges) yet sur- species in the two hemispheres. Here ters, and have even been sighted or changing conditions, and tolerating rounded by the highly unsuitable and we present some first results using established on some islands (UK, very different winter conditions in arid habitat of the Karoo (Samways Odonata species as model organisms. Ireland), as well as Scandinavia. comparison with those in summer 2008). There is no doubt, however, Recently, some African species have (Van Huyssteen & Samways 2009). that certain narrow-range endemic spe- Expansion of now also colonized southern Europe The greatly changing climatic condi- cies would be in a very precarious state geographical ranges of and are expanding their ranges north- tions from one year to the next, and should climate warming continue. One dragonfly species wards (Ott, this atlas, pp. 82f.). even one decade to the next, often species is the recently-discovered The expansion of geographical ranges The situation in southern Africa means that certain species retract their Syncordulia serendipator, which only lives of dragonfly species is well documented appears to be very different. One of geographical ranges in dry years, and in the high reaches of the Cape moun- then, opportunistically, expand again in tains, with no elevational flexibility wet years. One example, is the relative- should conditions become too severe. ly rare Orthetrum robustum, which retreats to permanent lake refugia in Changes in the wet years and then moves into recent- phenology of Odonata ly-flooded pans in wet years. Like the Changes of the dragonfly phenology also rare, Urothemis luciana, it is a strong are well documented in the northern flier and ready colonizer. Yet, of sur- hemisphere (Ott 2001, submitted, prise has been the movement capabili- Hassel et al. 2007): earlier emergence ties and ready establishment by seem- takes place and there is a clear tenden- ingly weak-flying damselflies. Lestes vir- cy to changes in voltism (e.g., a trend gatus has a very dynamic population to bivoltism in some species in north- spatial distribution, readily colonizing ern countries where these species for- new and appropriate ponds as formerly merly had only one cycle per year) and suitable ones dry out. Aciagrion congoense some species also show a prolonged showed even more extreme population flight season. If this process continues, spatial dynamics, moving south, over more and more de-synchronisation of some 300 km, to St Lucia in South emergence may occur (e.g., emergence Africa from Mozambique during the of spring species in late fall) which huge floods in the year 2000. Yet it had may have negative effects on the spe- never before been observed so far cies survival. Again, as with issues of south. Then, by 2005, it had disap- change in geographical range and in Figure 1. Dried out water body near Kaiserslautern (Germany) in 2006: once a habitat of the endangered peared again from St Lucia, during the elevation, the situation in the southern mooreland species Coenagrion hastulatum. Photo: J. Ott. dry phase of the climatic cycle. hemisphere is masked by great differ- ences in phenology, both in geographi- Expansion of cal area (Samways & Grant 2006) and dragonfly species to from year to year, with even overwin- higher elevations tering of some species from one year Besides geographical range expansion, to the next at sometimes but not at movements to higher elevations have others (Samways 2008). also been recorded, which has increased local Odonata diversity Species turnover of (Oertli et al. 2008). With continuing Odonata in water bodies climate change, there may also be a Monitoring in the northern hemisphere reduction of sensitive, montane species has shown that there is an increasing loosing their preferred biotopes in number of Mediterranean species higher elevations with a typical temper- dominating certain water bodies (Ott ature regime and with perhaps increas- submitted). ing predominance of habitat general- ists (Ott submitted). At least in the Effects of drying out southern hemisphere, it is difficult to of water bodies on the determine whether there has been an Odonata assemblages increase in elevational ranges of odo- Drying out of water bodies leads to a nates, as the background ‘noise’ of complete change, and even total elimi- prehistoric climate change and the cur- nation, of the Odonata assemblages. Figure 2. The parthenogenetic Crayfish Procambarus sp. – in Germany an alien species e.g. found in the rent strong climatic cycles appear to Short term drying out favours species Palatinate – preying upon a dragonfly larva (Libellula quadrimaculata). Photo: J. Ott. mask local anthropogenic effects. with high colonising ability and a short 84 ATLAS OF BIODIVERSITY RISK CHAPTER 3 life cycle (r-strategists, such as Ischnura many alien crayfish species – a conse- pumilio, Lestes barbarus, Libellula depressa) quence of stocking by fishermen, for but when water bodies dry out for commercial use, or set free by aquarists weeks or even months, the dragonfly – have now established as large popula- species – in particular, the species of tions in nearly all types of standing and running waters with long-lasting larval running waters. Alien invasive species, stages – are eliminated (Ott submitted). mostly alien trees, play a major role in As the southern hemisphere has been determining which dragonfly species subject to great variations in drought- can inhabit a particular water body, at ing and flooding from one year to the least in South Africa (Samways & next, the issue of odonate pond colo- Taylor 2004, Samways 2007). When the nization is more about spatial popula- alien riparian trees are removed, there tion dynamics and suitability of habitat is a rapid and significant recovery of than about gradual accumulation or the dragonfly fauna (Samways et al. loss of certain species. Certainly, there 2005). While no doubt the alien trees are no assembly rules for dragonfly change the water quality of the larval species establishing at new ponds, with habitat, by far the most significant fac- species arriving as and when conditions tor is the adverse effect of shade, Figure 3. Alien invasive and planted pine trees caused a major decline in dragonfly species by shading out the habitat. Endemic species like Syncordulia venator were locally extirpated. Shown here is the removal of the are suitable for them, and then leaving which has been shown to be experi- pines and the regrowth of the local fynbos vegetation. Photo: M. J. Samways. when conditions become unsuitable. mentally to be the critical factor. From circumstantial evidence, alien trout are Possible synergistic considered also to have an impact on References effects of climatic changes the southern hemisphere odonates in with intensive land-use and HASSEL C, THOMPSON DJ, FRENCH GC, HARVEY pies. – In: Cordero Rivera A. (Ed.), Forests montane areas. The evidence is not IF (2007) Historical changes in the phenolo- and Dragonflies. Pensoft Publishers, Sofia– emissions strong, but there have been instances gy of British Odonata are related to climate. Moscow, 209-224. The eutrophication and acidification as where certain endemic odonate species Global Change Biology 13: 933-941. SAMWAYS MJ (2008) Dragonflies and a result of ongoing emissions lead to a occur above waterfalls but not below OERTLI B, INDERMUEHLE N, ANGÉLIBERT S, Damselflies of South Africa. Pensoft continuous stress for aquatic biotopes them where trout are present. HINDEN H, STOLL A (2008) Publishers, Sofia–Moscow. Macroinvertebrate assemblages in 25 high SAMWAYS MJ, GRANT PBC (2006) Honing Red in the northern hemisphere, even if in alpine ponds of the Swiss National Park List assessments of lesser-known taxa in recent years in many areas water quality Which species / (Cirque of Macun) and relation to environ- biodiversity hotspots. Biodiversity and has improved. species groups are at risk? mental variables. Hydrobiologia 597(1): 29-41. Conservation 16: 2575-2586. In both the northern and southern OTT J (2001) Expansion of mediterranean SAMWAYS MJ, TAYLOR S (2004) Impacts of Possible synergistic effects of hemispheres, the species most at risk Odonata in Germany and Europe – invasive alien plants on red-listed South climatic changes with alien consequences of climatic changes – African dragonflies (Odonata). South African are those of sensitive habitats – such Adapted behaviour and shifting species invasive species Journal of Science 100: 78-80. as moorland and montane species, as ranges. S. – In: Walter G-R et al. (Eds), SAMWAYS MJ, TAYLOR S, TARBOTON W (2005) To date, little is known of synergistic well as species requiring stable environ- “Finger prints” of Climate Change. Kluwer Extinction reprieve following alien removal. effects in the northern hemisphere, but mental conditions (e.g., water level).