«Taxonomic Revision, Molecular Phylogeny and Zoogeography of the huntsman spider genus Eusparassus (Araneae: Sparassidae) Dissertation for attaining ...»
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Molecular phylogeny of Sparassidae with focus on Eusparassus and Eusparassinae This chapter is based on the following manuscript in a slightly modified version.
Status: under review (second round) Type of publication: Research article Journal: Molecular Phylogenetics and Evolution Citation: Moradmand, M., Schönhofer, A. L., Jäger, P., 2013. Molecular phylogeny of the huntsman spider family Sparassidae with focus on the genus Eusparassus and notes on the RTA-clade and ‘Laterigradae’. Molecular Phylogenetics and Evolution, under review.
Results: chapter 3.3: Molecular phylogeny
The molecular phylogeny of the huntsman spider family Sparassidae is comprehensively investigated for the first time using four molecular markers (mitochondrial COI and 16S; nuclear H3 and 28S). Sparassidae was recovered as monophyletic and as most basal group within the RTA-clade. No affiliation to other members of the ‘Laterigradae’ (Philodromidae, Selenopidae and Thomisidae) was observed, the crab-like posture of this group is assumed a result of convergent evolution. Only the families Philodromidae and Selenopidae were found members of a supported clade together with Salticidae and Corinnidae, while Thomisidae was nested within the higher Lycosoidea. Including a considerable amount of RTA-representatives, the higher-level clade Dionycha was not supported monophyletic. Within Sparassidae monophyly of the subfamilies Heteropodinae sensu stricto, Palystinae and Deleninae was recovered. Sparianthinae was supported as the most basal clade, diverging considerably early from all other Sparassidae.
Sparassinae and the genus Olios were found to be polyphyletic. Eusparassinae was not recovered monophyletic, with the two original genera Eusparassus and Pseudomicrommata in separate clades and only the latter clustered with most other assumed Eusparassinae, here termed the “African clade”. Further focus was on the monophyletic genus Eusparassus and its proposed species groups, of which the dufouri-, walckenaeri- and doriae-group were recovered monophyletic with the latter two groups more closely related. The divergence time of Sparassidae and the genus Eusparassus were estimated with 186 and 70 million years ago respectively according to molecular clock analyses. An African origin of Eusparassus in Namib Desert was proposed.
Keywords: Sparassidae classification; Eusparassinae; Sparassinae, Heteropodinae, Palystinae, Sparianthinae, Dionycha; molecular dating
Spiders are the second most diverse order in the Arachnida and important and abundant predators in most terrestrial habitats (Foelix, 2010). Hence it is rather surprising that to date only a small fraction of their diversity has been included in studies on phylogenetic systematics (Agnarsson et al., 2013b; Arnedo et al., 2009; Hedin and Bond, 2006; Miller et al., 2010). Yet, phylogenetic information is lacking for entire families or includes only few representatives of families of up to thousand species. Within such a framework many phylogenetic hypotheses remain to be tested.
Among the currently known families of entelegyne spiders, the families Sparassidae Bertkau, 1872 (giant crab spiders or huntsman spiders), Selenopidae Simon, 1897 (wall crab spiders or flatties), Philodromidae Thorell, 1870 (running crab spiders) and Thomisidae Sundevall, 1833 (“true” crab spiders) share the character of laterigrade legs, that is characterised by a crab-like posture (Latreille, 1802). The characteristic leg position and crab-like locomotion enables laterigrades to manoeuvre more quickly and take refuge in even narrow crevices. Upon this easy to see character Latreille (1802) proposed the name ‘Laterigradae’ (sub “Latérigrades”) for this group of taxa and Simon (1864) used an alternative term “Thomisiformes” for grouping the very same families. Coddington and Levi (1991) followed Latreille and Simon in assuming close phylogenetic relationship, although they noted that homoplasy could be possible. Prior to them, Homann (1971) studied the morphology of the eyes, and found Sparassidae and Philodromidae to have a similar eye structure that is different from Selenopidae. According to these eye structures, Homann (1975) proposed Sparassidae as sister to Philodromidae, and also related Thomisidae with the Lycosoidea. Bayer and Schönhofer (2013) recovered Thomisidae in an uncertain position as either sister group or part of Lycosoidea. Up to date there have been no molecular phylogenetic studies focusing on the inter-familial relationships of these laterigrades, but a few studies explored intra-familial relationships within Selenopidae (Crews and Gillespie, 2010;
Crews et al., 2010), Thomisidae (Benjamin et al., 2008) and Sparassidae (Agnarsson and Rayor, 2013). The Philodromidae have not been subject of any molecular phylogenetic studies; except for being treated as outgroup.
Results: chapter 3.3: Molecular phylogeny
FIGURE 1. The present concept of Sparassidae relationships (modified after Jäger, 1998), with genera included in this study given in bold and larger.
The geographic distribution of the groups is indicated at the branches or stated with the genera: AF (Africa), AM (America), AS (Asia), AU (Australia), EU (Europe) and MA (Madagascar).
Results: chapter 3.3: Molecular phylogeny
1.2. Family Sparassidae and its phylogenetic placement
The cosmopolitan family of huntsman spiders, Sparassidae, is composed of small to very large hunting or ambushing spiders (Jäger, 2001). They inhabit a wide variety of mainly tropical to subtropical habitats, ranging from true deserts and semi-deserts over a wide variety of woodland and forest formations up to mountainous highlands (Hirst, 1992; Jäger and Kunz, 2005;
Lawrence, 1962; Moradmand, 2013; Rheims, 2010a, b). Frequently recorded from caves (Jäger, 2012; Moradmand and Jäger, 2011), members from South East Asian caves represent the largest known living spiders in terms of leg-span (Jäger, 2005). Sparassidae currently comprises 85 genera and 1132 described species (Platnick, 2013) and the family thus represents one of the most diverse and successful groups of araneomorph spiders. The proposed synapomorphy of Sparassidae is the presence of soft trilobate membranes at the tip of the metatarsi of the walking legs (Petrunkevitch, 1928), which enable better mobility of the tarsi (Clarke, 1984). As another characteristic in Sparassidae Simon (1892: 26, fig. 40) found the tips of the claw tuft setae indented. Homann (1971) suggested the presence of a split rhabdome may be an additional synapomorphy, but studied the pigmentation and structure of the secondary eyes of only a few Sparassidae genera. Within the Entelegynae assemblage of Araneomorphae, Sparassidae are members of the RTA-clade, which are distinguished by the presence of a retrolateral tibial apophysis (RTA) on the pedipalps of males (Coddington and Levi, 1991). Within the RTA-clade Coddington and Levi (1991) and Coddington (2005) treated Sparassidae as a member of Dionycha. The Dionycha clade is solely characterised by its members having two-clawed tarsi and the group is currently composed of several heterogeneous spider families, with its monophyly still largely untested (Agnarsson et al., 2013b; Coddington, 2005).
1.3. Sparassidae subfamilies
Simon (1897, 1903) and Järvi (1912, 1914) were the main contributors towards a classification of Sparassidae into subfamilies. Simon (1897) treated Sparassidae as a subfamily of Clubionidae, and further classified “Sparassinae” into seven sub-groups (Sparasseae, Heteropodeae, Palysteae, Staianeae, Spariantheae, Clastieae and Chrosiodermateae) using somatic characters, mainly those concerning eye morphology (arrangement and size). Hogg (1903) proposed an additional subfamily Deleninae for some Australian endemics. Simon (1903) placed the genera previously classified as Sparassinae into Deleninae and proposed a new subfamily Tibellomatinae for a
Results: chapter 3.3: Molecular phylogenymonotypic genus based on a juvenile. Järvi (1912, 1914) was the first author who validated Sparassidae as a family. His classification exclusively emphasised characters of the female copulatory organs to propose two new subfamilies (Eusparassinae, Polybetinae) and used Micrommatinae for Sparassinae. These traditional classifications are still considered valid with modifications by Petrunkevitch (1928) and Roewer (1954). In his classification of Sparassidae subfamilies Petrunkevitch (1928) gave priority to somatic characters proposed by Simon. He partially rejected Järvi’s classification and included Polybetinae and Deleninae in Eusparassinae.
Croeser (1996) revised the Palystinae, but only proposed the transfer of a few genera between subfamilies. Jäger (1998) revised the character states of the subfamilies and recognized synapomorphies for Heteropodinae and Sparianthinae. He stated the status of the remaining subfamilies was far from resolved. Rheims (2007) provided a first morphological cladistics analysis, but due to subsequenly altered coding of several characters she asked to refrain from comparison (C. A. Rheims personal communication). Agnarsson and Rayor (2013) investigated the inter-generic phylogenetic relationships of the Australian Deleninae and proposed them monophyletic, although based on sparse outgroup sampling. Currently, the status of the remaining proposed subfamilies is weakly supported. The current classification concept of Sparassidae modified after Jäger (1998) is presented in Figure 1.
1.4. Eusparassus and Eusparassinae
The genus Eusparassus Simon, 1903 is the sixth largest genus of the family Sparassidae (Platnick, 2013) and include species which are among the most significant arthropod predators in dry and semidry areas of Africa and Eurasia (Levy, 1989; Moradmand and Jäger, 2012a;
Moradmand, 2013). It is also a useful group for investigating phylogenetic relationships and historical biogeography within Sparassidae, as it was recently revised on a global scale (Moradmand and Jäger, 2012a; Moradmand, 2013) and contains the only well assignable fossil of the family. The minimum age of Eusparassus is currently dated back to the Eocene, about 44-49 MA, based on the conspicuous and well preserved E. crassipes (Koch and Berendt, 1854) found in northern European Baltic amber (Dunlop et al., 2011). Extant Eusparassus include 30 species, of which 27 are assigned to six species-groups namely the dufouri-, walckenaeri-, doriae-, tuckeri-, jaegeri- and vestigator-groups (Moradmand, 2013). Aside from the description of several new species, most transfers were from the genus Olios Wackenaer, 1837 to Eusparassus or vice versa (Jäger et al., 2002; Moradmand and Jäger, 2012a; Moradmand, 2013). Simon (1897)
Results: chapter 3.3: Molecular phylogenyfirst placed species of Eusparassus (at that time still in Sparassus) in Sparassinae. After describing Eusparassus, Simon (1903) transferred the genus with other Sparassinae into the Deleninae. Järvi (1912) proposed the new subfamily Eusparassinae for Eusparassus, Pseudomicrommata Järvi, 1914 and Rhitymna Simon, 1897, although Rhitymna, was later proposed to be misplaced (Jäger, 2003). Eusparassinae was reaffirmed by Jäger and Kunz (2003), who outlined some synapomorphies for the subfamily and suggested that further African genera should be included (see Figure 1). The monotypic genus Cercetius Simon, 1902 is likely to be a synonym of Eusparassus (Moradmand and Jäger, 2012b) and a formal case proposal was made to ICZN (International Commission on Zoological Nomenclature) to give Eusparassus precedence.
Until a final decision usage of both names is retained (ICZN, 1999: Article 82). Cercetius perezi could not be affiliated to any species-group proposed by Moradmand (2013).
1.5. Aims of this study Similarity of morphological traits among different lineages of organisms is not necessarily explained by sharing a common ancestor, but may as well be the result of convergent evolution (Revell et al., 2007). Various evolutionary processes, such as occupying similar habitats (Johnson et al., 2009), are known to cause phenotypic similarity (Bertossa, 2011). Phylogenetic methods have been applied to test characters assumed as diagnostic for the members of the order Araneae (e.g. Miller et al., 2010). However, the present classification still relies on many morphological traits that have yet to be investigated to discriminate between homology and convergence.