Modisiminae Simon, 1893

Huber, Bernhard A., Eberle, Jonas & Dimitrov, Dimitar, 2018, The phylogeny of pholcid spiders: a critical evaluation of relationships suggested by molecular data (Araneae, Pholcidae), ZooKeys 789, pp. 51-101 : 57-60

Subfamily Modisiminae Simon, 1893 Figs 3, 4, 5

Modisimeae Simon, 1893: 484. Type genus Modisimus Simon, 1893, by subsequent designation ( Huber 2011b).

Modisiminae Simon; Huber 2011b: 216.

Remarks.

Modisiminae are the typical pholcids of the humid Neotropics, where they occupy a wide variety of microhabitats from leaf litter to high among the vegetation. This ecological variability is paralleled by a wide range of body forms, from tiny ground-dwelling forms (e.g., Gertsch 1982, Huber and Rheims 2011) to some of the largest pholcids with leg spans of over 15 cm (e.g., Huber and Astrin 2009, Huber 2015, 2018). With currently 480 species in 24 genera, Modisiminae is one of the two large subfamilies of Pholcidae , with several species-rich genera (e.g., Anopsicus Chamberlin & Ivie, 1938; Psilochorus Simon, 1893; Modisimus Simon, 1893; Mesabolivar González-Sponga, 1998; Carapoia González-Sponga, 1998) and many undescribed species.

All previous analyses have supported this group ( Huber 2000, 2001, Bruvo Mađarić et al. 2005, Dimitrov et al. 2013), even though with minor differences in composition. The equivalent 'New World clade’ in Huber (2001) still included the Australian Wugigarra , a genus that has since been moved to Arteminae ( Dimitrov et al. 2013). As a result, Modisiminae is now considered to be restricted to the New World.

Our analyses all recover Modisiminae , but with very low support values. This is possibly due to the mysterious Andean genus Priscula Simon, 1893 (Figure 3) that is either included in Modisiminae (IQ-TREE) or not (RAxML). The position of Priscula has always been considered problematic. Simon (1893) created a separate taxon “Prisculeae” for this genus; Brignoli (1981) synonymized it with Physocyclus ; the first morphological cladistic analysis ( Huber 2000) supported the position of Priscula near Physocyclus but this result was explicitly doubted ( Huber 2000: 129). In the molecular analysis of Dimitrov et al. (2013) Priscula was excluded because the positions of the included species varied dramatically among different types of analyses. Morphologically, Priscula differs from (other) Modisiminae by the presence of ALS piriform gland spigots and by the absence of a retrolateral apophysis on the male palpal coxa ( Huber 2000), i.e., it has retained plesiomorphic characters. A sister-group relationship between Priscula and other Modisiminae appears thus plausible from a morphological point of view.

Despite the low support values, we thus consider Modisiminae (including Priscula or not) a likely monophyletic group. Several morphological characters support Modisiminae (incl. Priscula ): an exposed tarsal organ; the reduction of epiandrous spigots (shared with 'other Arteminae '; see above); and a large distance between ALE and PME ( Huber 2000). As indicated above (section Arteminae ) our data weakly support a sister-group relationship between 'other Arteminae ' and Modisiminae .

Within Modisiminae , many support values are extremely low, and the suggested relationships are thus unreliable (Figure 3). In addition, taxon sampling is very uneven, with some genera well represented (e.g., Carapoia , Mesabolivar , Modisimus ), and others poorly represented or entirely missing (see below). However, several results are consistent among analyses and noteworthy for various reasons: they suggest groups that appear feasible in terms of biogeography; they suggest interesting evolutionary scenarios; and they suggest formal taxonomic changes, some of which have been suggested before based on morphology.

Apart from Priscula , the ‘basal’ branches within Modisiminae lead to small South American unnamed taxa (Figure 3). In particular, the two species “Br16-44” and " MACN270" are both tiny, with body lengths of 0.9 and 1.3 mm, respectively. Other ‘basal’ branches lead to an unnamed Amazonian genus ( “Br16-178” and “Br16-50”; body lengths: 1.5-1.8 mm) and the Atlantic Forest genus Tupigea Huber, 2000 (body lengths: 1.3-1.9 mm; Huber 2000, Huber and Rheims 2011). This suggests a similar evolutionary scenario as proposed for 'other Arteminae ' above, i.e., that ancestral Modisiminae may have been small ground-dwelling species. Priscula is once again the disturbing factor in this scenario: all known representatives of Priscula are medium-size to large spiders ( Huber 2000), possibly surpassed (as far as body mass is concerned) by Artema only. In both Arteminae and Modisiminae , the emerging picture is one of medium-sized forms missing or disappearing early, large forms experiencing little subsequent changes in body shape and poor subsequent speciation ( Artema : currently eight species; Priscula : currently 17 species), and small forms diversifying dramatically in size, shape, and numbers ('other Arteminae ': currently 91 species; Modisiminae without Priscula : currently 463 species).

The next branch (Figure 3; Chibchea Huber, 2000 to Pisaboa Huber, 2000) includes several South American genera, some of them diverse but poorly represented in our analyses (e.g., Chibchea ). The close relationship between Pisaboa and Waunana Huber, 2000 was already suggested in the original descriptions of these genera ( Huber 2000), even though based on highly homoplastic characters (vertical hairs on male leg tibiae in high density; shape of apophysis on male palpal femur). A close relationship of these two genera with Chibchea either receives very low support (IQ-TREE, RAxML) or is not recovered (RogueNaRok); it is neither supported nor contradicted by morphology. Clearly, this clade needs a much denser sampling and the addition of missing taxa that are possibly related (e.g., Pomboa ).

The next clade (Figure 3) includes all North and Central American and Caribbean taxa, suggesting that the ancestor of this clade arrived in the region from South America. This scenario was explicitly rejected by Dimitrov et al. (2013) based on the supposed age of the group (~120-170 Ma). However, our upcoming analysis has not been able to confirm this age ( Eberle et al. 2018; we were not able to calculate convincing absolute ages from the data). The clade is recovered in most analyses (it is paraphyletic in the 4+ genes tree) but always with low support (only SH values are reasonable to high). The only geographic outlier in this clade is South American ' Psilochorus '. North American ( ‘true’) Psilochorus and South American ' Psilochorus ' each receive high to full support but are never resolved as sister taxa. Whether South American ' Psilochorus ' are ancestral within this large clade or represent a case of back-colonization is currently impossible to say; the internal nodes in this clade have partly too low support to favour a particular scenario. The inclusion of the Central American Ixchela Huber, 2000 in this clade fits the geographic pattern and contradicts a previous speculation (in Huber 2000) that Ixchela might be close to the South American genus Aymaria Huber, 2000. In much the same way, the only Central American representative of Coryssocnemis Simon, 1893 included in our analyses is placed in this group, far away from ‘true’ South American Coryssocnemis (the polyphyly of Coryssocnemis has long been suspected: Gertsch 1971, Brignoli 1981, Huber 1998, 2000). The Cuban endemic genus Platnicknia Özdikmen & Demir, 2009 is deeply nested within the large genus Modisimus . It is resolved as sister to a distinctive group of Hispaniolan leaf-dwelling representatives of Modisimus (the "leaf-dwelling species group" in Huber et al. 2010) and synonymized below. Finally, the large genus Anopsicus (63 described species) is poorly represented in our analyses. The three species included are all undescribed, do not group together, and are nested among Modisimus . Since neither the type species of Anopsicus is included nor is a potential close relative (or at least another species from Yucatán), the monophyly and position of Anopsicus both remain dubious.

Sister to the previous North and Central American and Caribbean clade is another large, entirely South American clade (Figure 3, bottom). The sister-group relationship is very poorly supported, but the monophyly of the South American clade has modest (4+ genes) to reasonable (RogueNaRok) support. It is divided into three subclades with reasonable to full support plus the genus Aymaria that is represented by a single species and whose position within this clade is not convincingly resolved. The first subclade included is here informally called the ' Mesabolivar clade’ (Figure 4); the second subclade is largely Venezuelan and thus called 'Venezuelan clade’ (Figure 5); the third subclade is the genus Carapoia (Figure 5).

Within the ' Mesabolivar clade’ (Figure 4), our analyses suggest two specific relationships that are likely to have drastic taxonomic consequences. First, Litoporus Simon, 1893 is nested among ‘true’ northern South American Mesabolivar . This has been suggested before ( Dimitrov et al. 2013), but that previous analysis included a single species of Litoporus whose generic identity was uncertain ( Huber et al. 2013). The present analyses include several unambiguous (Amazonian) representatives of Litoporus . Our data support the monophyly of Litoporus (full support) but also its position within Mesabolivar (reasonable to high support). Second, Mesabolivar is composed of two sub-clades: ‘true’ northern South American Mesabolivar , and southern South American (largely Atlantic Forest) ' Mesabolivar '. The southern sub-clade includes the monotypic genus Teuia Huber, 2000 (synonymized with Mesabolivar in Huber 2018; the type species of Teuia is not included but a putatively closely related species: M. sepitus ). Potential formal taxonomic changes are discussed in the Taxonomy section below. The close relationship between Otavaloa Huber, 2000 and Mesabolivar is neither supported nor contradicted by morphological data.

The 'Venezuelan clade’ (Figure 5) receives high to full support and is composed of several genera that are either known from Venezuela only ( Systenita Simon, 1893, Stenosfemuraia González-Sponga, 1998), from Venezuela and Trinidad and Tobago ( Coryssocnemis ), or from Venezuela plus neighboring countries ( Mecolaesthus Simon, 1893). A close relationship among these genera had been suspected before based on morphology ( Huber 2000), and molecular data have always supported this ( Bruvo-Mađarić et al. 2005: 28S data and combined analysis; Dimitrov et al. 2013). Our data suggest that Coryssocnemis may be nested within Mecolaesthus , but our taxon sampling is weak, the topology is unstable ( Systenita is either nested within Mecolaesthus or not), and several internal nodes in the clade have low support. Formally, Coryssocnemis still includes several obviously misplaced species: several Central American species (see above), and several Atlantic Forest (Brazilian) species whose identity is probably impossible to resolve (poor descriptions, lost types; see Huber 2000, 2018).

The third subclade in the South American clade is Carapoia (Figure 5). Unlike Mesabolivar it is monophyletic and apparently less problematic, but just as Mesabolivar , the genus has become very difficult to diagnose, mainly because of ‘untypical’ species added to the genus based in large part on the present molecular data ( Huber 2018). Both for Mesabolivar and Carapoia our analyses suggest several species groups that are also supported by morphological data. For a detailed discussion of these groups, see Huber (2018).