Molecular Ecology (2010) 19, 3840–3841

NEWS AND VIEWS

PERSPECTIVE as a powerful tool for , as it allows us to distin- guish species and to discover new ones, using genetic (or Three sisters in the same dress: cryptic molecular) information. However, a current standard is speciation in African odonates that DNA alone should not be the unique source of infor- mation for species designations and that diagnostic charac- A. CORDERO-RIVERA and M. O. LORENZO- ters from classical taxonomic approaches (morphology, CARBALLA ecology) should be used to infer the rank of populations Grupo ECOEVO, Universidade de Vigo, EUET Forestal, (DeSalle et al. 2005). Campus Universitario, 36005, Pontevedra, Galiza, Spain The work of Damm et al. (2010) is based on the ‘taxo- nomic circle’ proposed by DeSalle et al. (2005), a term The discovery of cryptic species (i.e. two or more distinct which designs a methodology for new species discovering but morphologically undistinguishable species) has that combines traditional taxonomic work with the power grown exponentially in the last two decades, due mainly of modern molecular tools. The main idea within the con- to the increasing availability of DNA sequences. This cept is to ‘break’ the circle of tautological reasoning, i.e. suggests that hidden in the known species, many of taxonomists should use information based on geography which have been described based solely on morphologi- (or morphology, or other relevant discipline) to generate a cal information, there might be a high number of species null hypothesis. Then, this hypothesis is tested with rele- waiting to be discovered. In this issue Damm et al. vant information on the geographical distribution, mor- (2010) use a combination of genetic, morphological and phology, ecology, reproduction and behaviour of the ecological evidence to identify the first cryptic species putative taxa, integrated in the circle. Only when at least complex found within dragonflies ( order ). two lines of evidence support the presence of several taxa, Their findings add more evidence for the importance of are these entities recognized as species and the circle is combining information from different disciplines to new broken [see DeSalle et al. (2005) for more details]. species’ discovery (DeSalle et al. 2005). Damm et al. (2010) initially started a population genetic study in the African libellulid dragonfly stictica Received 8 April 2010; revision received 13 May 2010; accepted (for Trithemis spec. nov. see Fig. 1) but, surprisingly, three 17 May 2010 genetically distinct clusters were found, based on genetic evidence from NDI (NADH dehydrogenase 1) and COI (cytochrome c oxidase subunit I). Genetic distances The rapid increase of natural ecosystems destruction has between the clades were surprisingly high (5–9%), whereas leaded to the extinction of a great number of species. distance within clades was low (0–1%). Individuals of two Because most species are still undescribed, cataloging and of the clades occurred sympatrically in one site in explaining current diversity is the focus of much active (Popa Falls, Fig. 2). research. One of the immediate consequences of these efforts has been an increase in the research on cryptic spe- cies over the past two decades, mainly due to the increas- ing availability of DNA sequences. The identification and description of cryptic species provides opportunities to study important mechanisms of speciation, mate recogni- tion and natural resource protection and management (Bickford et al. 2007). The biological species concept, defined and elaborated mainly by Enrst Mayr (1996) defines species as ‘groups of interbreeding natural populations that are reproductively isolated from other such groups’. Under this concept, new species are formed when they are reproductively isolated. However, as mechanisms of reproductive isolation differ among taxa, no universal criterion to delimit species exists yet. DNA barcoding (i.e. the generation of DNA sequences for all named species on the planet) has recently emerged Fig. 1 A male of Trithemis sp., from Popa Falls in Namibia, Correspondence: A. Cordero-Rivera, Fax: (34) 986 801 907; where the two new taxa identified by Damm et al. (2010) coex- E-mail: [email protected] ist (Photo: A. Cordero-Rivera).

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African odonates have generated several surprises on what a species is and how to delimit them. Very recently, close examination of one of the commonest African dragon- flies, Brachytemis leucosticta, showed that it included two morphological types. In this case males are distinguished by coloration and morphology, but females are not (Dijkstra & Matushkina 2009). A different example where two species were hidden under one name was shown in Palpo- pleura lucia and P. portia. Here two male morphs were con- sidered to be ‘male polymorphism’ for centuries, until a difference in DNA sequences shed light on the erroneous species delimitations (Mitchell et al. 2006). The study of Damm et al. (2010) shows the importance of a detailed analysis of species diversity, especially in tropical countries, where threats to conservation make this Fig. 2 The typical habitat of the new species of Trithemis at task more urgent. Popa Falls, Namibia (Photo: A. Cordero-Rivera). This study also exemplifies the methodology proposed by DeSalle et al. (2005) and provides a good guidance This finding was the basis for the hypothesis of three when perplexing and unexpected results are found: rather cryptic species in T. stictica, which was tested by using the than trying to find ad-hoc explanations for new, unforeseen ‘taxonomic circle’ of DeSalle et al. (2005), including infor- results, use them to inspire new ideas. Then, test these mation on genetics, morphology and ecology of the differ- ideas with new, independent evidence (Johnson 2002). If ent clades found. the results were spurious, the new evidence will show that. Phylogenetic analyses corroborated the results of the dis- If not, a little step in the right direction has been made. tance analyses and separated individuals into three clades: clade 1 grouped together with other Trithemis species References according to the classical taxonomy of T. stictica and thus it was identified as the originally described T. stictica. Clades Bickford D, Lohman DJ, Sodhi NS et al. (2007) Cryptic species as a 2 and 3 appeared as sister species, with high phylogenetic window on diversity and conservation. Trends in Ecology and Evolution, 22, 148–155. support. Furthermore, the three clades are distinguishable Corbet PS (1999) Dragonflies. Behaviour and Ecology of Odonata, by unambiguous diagnostic characters (or barcodes). p. 463. Harley Books, Essex UK. A re-examination of 43 male specimens, previously Co´rdoba-Aguilar A (2008) Dragonflies and Damselflies. Model Organ- genetically characterized, showed consistent differences in isms for Ecological and Evolutionary Research. Oxford University morphology between the clades. The ‘true’ T. stictica can Press, Oxford, UK. be distinguished from clades 2 and 3 by eye and base wing Damm S, Schierwater B, Hadrys H (2010) An integrative approach coloration, as well as by differences in penis structure. to species discovery: from character-based DNA barcoding to Clades 2 and 3 are distinguished only by size. ecology. Molecular Ecology, 19, 3881–3893. Finally, an analysis of ecological patterns revealed differ- DeSalle R, Egan MG, Siddall M (2005) The unholy trinity: taxon- ences in habitat preferences among the three genetic clades, omy, species delimitation and DNA barcoding. Philosophical Transactions of the Royal Society B: Biological Sciences, 360, 1905– suggesting again that several taxa were involved in this 1916. system. Dijkstra K-DB, Matushkina N (2009) Kindred spirits: ‘‘Brachythemis In summary, significant genetic isolation, differences in leucosticta’’, Africa’s most familiar dragonfly, consists of two spe- habitat preferences, fixed size differences and reproductive cies (Odonata: ). International Journal of Odonatology, isolation together provide evidence to support the hypothe- 12, 237–256. sis of two new sympatric Trithemis species, which shows Johnson DH (2002) The importance of replication in wildlife the importance of combining information from different research. Journal of Wildlife Management, 66, 919–932. disciplines to define species limits (Damm et al. 2010). Mayr E (1996) What is a species, and what is not? Philosophy of Odonates have been used for decades as model systems Science, 63, 262–277. for many evolutionary and ecological studies (Co´rdoba- Mitchell A, Samways MJ (2005) The morphological ‘forms’ of Pal- popleura lucia (Drury) are separate species as evidenced by DNA Aguilar 2008). Their elaborate mating behaviour, which sequencing (Anisoptera : Libellulidae). Odonatologica, 34, 173– includes in some cases a complex courtship, based on 178. visual displays and their powerful flight (Corbet 1999) a priori suggest that cryptic speciation is unlikely to occur in doi: 10.1111/j.1365-294X.2010.04721.x this insect group. This work by Damm et al. (2010) demon- strates that these prejudices are no longer justified.

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