Dysdera

Bellvert, Adrià, Pollock, Laura J., Kaliontzopoulou, Antigoni & Arnedo, Miquel A., 2025, Tempo and mode of diversification of the red devil spiders (Araneae: Dysderidae) of the Canary Islands, Zoologica Scripta 54 (3), pp. 406-420 : 415

4.1 | The diversification mode of Canarian Dysdera spiders

An early increase in species diversification, followed by a decrease in net speciation rates towards the present is the trademark of an adaptive radiation process ( Glor, 2010; Losos & Mahler, 2010; Phillimore & Price, 2008). Declining diversification rates through time are generally interpreted as the results of early occupation of vacant niches until their saturation, which leads to the slowdown of cladogenetic events ( Gavrilets & Vose, 2005; Schluter, 2000). Such a pattern has been usually described by means of linage-through-time plots ( Nee et al., 1992; Pybus & Harvey, 2000), with density-dependent models describing this asymptotic accumulation of lineages through time (e.g. Linder & Bouchenak-Khelladi, 2017; Pincheira-Donoso et al., 2015). The early increase in a number of lineages and the corresponding negative γ values revealed for the Dysdera species from the Canary Islands points towards a rapid filling of ecological niches and a deceleration of speciation rates over time, as also seen with the time-dependent model of diversification. Interestingly, the Canary Islands may have also presented additional episodes of ecological opportunity as new islands emerged over time, which can be reflected in diversification pulses in the LTT plot ( Pincheira-Donoso et al., 2015). Such pulses can be identified in Figure 2b. Multirate variants of the pure birth model lend further support to this observation, as they exhibited overlapping AIC values when accounting for the phylogenetic uncertainty, however, their mean values have been slightly higher than the density-dependent model. Obviously, undiscovered species could compromise these results, as incompleteness in the taxon sampling could mirror a similar pattern as the density-dependent speciation ( Rabosky & Lovette, 2008). However, given the solid taxonomic ground established by a series of modern taxonomic treatments of the group (e.g. Arnedo et al., 2000; Arnedo & Ribera, 1996, 1997, 1999; Bellvert et al., 2023; Macías-Hernández et al., 2010), we doubt that the number of undiscovered species may actually affect our main conclusions.