Modisimus, SIMON, 1893

Huber, Bernhard A., Fischer, Nadine & Astrin, Jonas J., 2010, High level of endemism in Haiti’s last remaining forests: a revision of Modisimus (Araneae: Pholcidae) on Hispaniola, using morphology and molecules, Zoological Journal of the Linnean Society 158 (2), pp. 244-299 : 251-255

publication ID

https://doi.org/ 10.1111/j.1096-3642.2009.00559.x

persistent identifier

https://treatment.plazi.org/id/03D3130F-7A3F-743D-DCA4-BF13FC714637

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Valdenar

scientific name

Modisimus
status

 

MODISIMUS SIMON, 1893

Type species: Modisimus glaucus Simon, 1893 ; Modisimus dilutus Gertsch, 1941 of Modisimops ; Hedypsilus culicinus Simon, 1893 of Hedypsilus . Modisimus Simon, 1893b: 484–485 ; Gertsch, 1971: 66;

Brignoli, 1973: 219–221 (synonymy of Modisimops );

Gertsch & Peck, 1992: 1192–1193 (synonymy of

Modisimops with Hedypsilus ); Huber, 1996: 238–

239 (synonymy of Hedypsilus ); Huber, 1998: 21–33. Hedypsilus Simon, 1893b: 484–486 . Modisimops Mello-Leitão, 1946: 50 .

Type species: The identity of the type species, M. glaucus , is problematic, but it is almost certainly part of the group referred to here as the femoratus group. The single available female type specimen ( MNHN AR 10535) is in poor condition, and the type locality is poorly specified. The original Latin description ( Simon, 1893a) says ‘Ins. S.-Domingo et ins. S.-Thomas’; in the Histoire Naturelle, Simon (1893b) lists ‘Saint-Domingue’, Saint-Thomas, and Jamaica. Saint-Domingue was the name of the French colony that is now Haiti, and the name continued to be used until the 20 th century. Saint-Domingue and Santo Domingo have also sometimes been used to refer to all of Hispaniola, and even to the modern Dominican Republic (e.g. Fassig, 1929). Simon’s ‘Ins. S.-Domingo’ suggests that he referred to the entire island of Hispaniola. In any case, the previous statement ( Huber, 1996) that modern Santo Domingo (the capital of the Dominican Republic) is the type locality is mistaken.

Obviously, Simon (1893a, b, 1894) had specimens from various islands, and he considered them to be conspecific. The original description ( Simon, 1893a) is based on females only, and the later drawings of the male ( Simon, 1893b: figs 480, 485) do not resemble anything of what we have seen in Hispaniolan Modisimus . These drawings are thus probably based on specimens of other species, but the material seems to be lost. The only syntype specimen available at the MNHN, Paris, is a female, with Simon’s original label ‘6840 Mod. glaucus E.S. S°. Domingo’. Habitus, colour pattern, and especially the epigynum of this specimen resemble M. femoratus , as well as the closely related M. jima sp. nov. Both species are widely distributed in the Dominican Republic ( Fig. 195 View Figure 195 ), and are thus likely to have been collected previously. In the type specimen, the distinctive sclerite in front of the epigynum is mostly hidden in a fold, and lies close to the epigynum (rather as in M. jima sp. nov., cf. Fig. 39 View Figures 38–62 ). Further complicating the picture, specimens from near Puerto Plata, here assigned tentatively to M. femoratus , are also potential candidates for being M. glaucus (as suggested by Bryant, 1948). It may not be possible to finally resolve this problem, but the species of the femoratus group (especially the populations assigned tentatively herein) should be scrutinized in more detail before applying the type species name to one of them.

Diagnosis: Modisimus is traditionally diagnosed by the high elevation of the ocular area, the ‘eye turret’ ( Simon, 1893b; Gertsch, 1971; Brignoli, 1973; Huber, 1996, 1998, 2000). In many species this elevation is quite distinct ( Figs 28, 30, 32 View Figures 17–37 , 83–85 View Figures 83–93 ), but other species have elevations that are no higher than those of other New World genera ( Fig. 24 View Figures 17–37 ). In the absence of a comprehensive cladistic analysis of the entire genus, the polarity of this character remains an open question. Adding to the confusion, an undescribed Cuban species (Sancti Spiritus: Escambray, Topes de Collantes; specimens in ZFMK and Instituto de Ecología y Sistemática, Habana) has a very high eye turret, but otherwise closely resembles the New World genus Psilochorus (especially in the male palps; B. Huber, unpubl. data).

Another character that unites most but not all Modisimus species is the high density of short vertical hairs ( Fig. 121 View Figures 115–123 ) on the male leg femora, but not on the tibiae. Among the species described herein, only M. cienaga sp. nov. also lacks these hairs on the femora. The only other genus that shares such hairs on the femora ( Waunana Huber, 2000 ) also has them on the tibiae (like several other New World genera; Huber, 2000). As with the eye turret above, the polarity of this character remains unclear.

Description: The description given here only covers Hispaniolan representatives. Total body length ranges from 1 mm ( M. mango sp. nov. and M. cienaga sp. nov.) to over 4 mm ( Modisimus macaya sp. nov.), but most species are within the range of 2–3 mm. Carapace with median furrow ( Figs 86, 87 View Figures 83–93 ), either with or without median and lateral marks (e.g. Figs 27, 31 View Figures 17–37 ). Ocular area elevated, but ranging widely from slightly elevated ( Modisimus fuscus Bryant, 1948 and Modisimus epepye sp. nov.; Fig. 24 View Figures 17–37 ) to highly elevated ( M. vittatus , Fig. 32 View Figures 17–37 ). Distance between posterior median eyes ( PME – PME), 40–180 Mm; PME diameter, 55–170 Mm; PME –anterior lateral eye ( ALE), 45–210 Mm, anterior median eyes ( AME) mostly tiny (diameter about 20 Mm), in some cases apparently with pigment, but without lenses, and entirely reduced in M. cienaga sp. nov. and the leafdwelling species. Clypeus unmodified. Sternum never with frontal humps, often with distinct brown bands laterally ( Fig. 20 View Figures 17–37 ), or medially ( Fig. 29 View Figures 17–37 ), in M. toma sp. nov. females with two bundles of strong hairs posteriorly ( Fig. 118 View Figures 115–123 ). Male chelicerae mostly provided with modified (short and strong) hairs, pointed or club-shaped (e.g. Figs 88–91 View Figures 83–93 ), often on elevations (spectacular in M. toma sp. nov.; Figs 91 View Figures 83–93 , 134 View Figures 130–135 ), rarely with apophyses ( Figs 143 View Figures 142–147 , 193 View Figures 190–194 : M. fuscus , Modisimus paraiso sp. nov.), or unmodified ( M. epepye sp. nov., M. cuadro sp. nov., M. pelejil sp. nov., and M. cienaga sp. nov.). Male palps with retrolateral coxa apophysis, ventral femur apophysis, procursus often with dorsal spine-like process ( Figs 94–96 View Figures 94–103 ), and bulb with strong apophysis.

Abdomen mostly oval and pointed at spinnerets ( Figs 19, 28 View Figures 17–37 ), rarely elongated (especially in M. kiskeya sp. nov., Fig. 20 View Figures 17–37 ; also M. femoratus and leafdwelling species, Figs 17, 35–37 View Figures 17–37 ), or globular (tiny leaf-litter species; Fig. 24–26 View Figures 17–37 ); in M. angulatus sp. nov. distinctively angular dorsally ( Fig. 21 View Figures 17–37 ); in M. roumaini sp. nov. and M. seguin sp. nov. with calluslike posterior area in males only ( Figs 27, 28 View Figures 17–37 ). Often with many dark marks, both dorsally and laterally. White or pale-bluish spots often arranged in lines ( Figs 30, 34 View Figures 17–37 ), but variable within species. Epigynum very variable among species in size and shape ( Figs 38–62 View Figures 38–62 ), often with strong hairs in distinctive groups, and often with paired or unpaired protrusions ( Figs 105–107, 110, 114 View Figures 104–114 ; mating plugs?). Internal female genitalia with highly diagnostic sclerites and pore plates ( Figs 63–82 View Figures 63–82 ), sometimes with large membranous frontal structure ( Figs 126 View Figures 124–129 , 132, 135 View Figures 130–135 ; femoratus group).

Most species are long-legged, with leg 1 between 7 and 14 times the body length; only M. fuscus , M. epepye sp. nov. and M. cienaga sp. nov. have considerably shorter legs (less than 5 times the body length). Tibia 1 length ranges from 1.4 mm ( M. cienaga sp. nov.) to 10.5 ( M. macaya sp. nov.), but is mostly between 4 and 8 mm. Tibia 2 can be slightly longer than tibia 4, but is shorter in all representatives of the southern paleoisland group, in M. epepye sp. nov., and in M. bachata sp. nov., and is considerably longer in M. cienaga sp. nov., and in the leafdwelling species. The length/diameter (L/d) of tibia 1 lies mostly between 40 and 80; only in M. fuscus , M. epepye sp. nov., and M. cienaga sp. nov., does it fall below 25. Spines are often present on femora 1 and 2, arranged in one to four rows, sometimes on elevated bases ( Fig. 119 View Figures 115–123 ; M. femoratus , M. kiskeya sp. nov.), and are highly variable within species (larger males tend to have more and stronger spines), and among close relatives. Retrolateral trichobothrium on tibia 1 mostly at 6–16%, positioned more distally in M. fuscus and M. epepye sp. nov. (23 and 25%, respectively), and in M. cienaga sp. nov. (31%). Prolateral trichobothrium usually missing on tibia 1, being present only in M. leprete sp. nov. (regained?!). Curved hairs ( Fig. 120 View Figures 115–123 ) often present on tibiae and metatarsi. Short vertical hairs on male femora, usually in high density ( Fig. 121 View Figures 115–123 ), missing only in M. cienaga sp. nov.

Sexual dimorphism slight: females often smaller, always with shorter legs, chelicerae never modified, and few vertical hairs on legs (almost none on femora). In two species, the female sternum is sexually modified ( M. toma sp. nov., with a pair of bundles of strong hairs posteriorly, Fig. 118 View Figures 115–123 ; M. enriquillo sp. nov., with a pair of apophyses posteriorly, Figs 49, 50 View Figures 38–62 ). In the leaf-dwelling species, the female clypeus is not darkened.

Diversity: In this study we redescribe three of the four previously described species and describe 22 new species. In addition, the AMNH and ZFMK collections contain seven further morphospecies from Hispaniola (five of them from Haiti). These are either poorly preserved or represented by a single female specimen only, and are therefore not described.

Habitat and web: Most species are restricted to forests, where they typically build dome-shaped webs, with a tangle of lines above ( Figs 11–14 View Figures 5–16 ), in sheltered spaces under logs and rocks, in cavities, or between buttresses. Some species live close to the ground, under suitable leaves that are curved in a way to allow for web building. Among these, M. cienaga sp. nov. appears to differ from all known Hispaniolan congeners, in that it seems to build no or just a minimal web, and runs quickly when disturbed (cf. M. culicinus ; Huber, 1996). Some species build their webs higher up in the vegetation, up to 2 m above the ground (especially M. kiskeya sp. nov., M. vittatus , and the leaf-dwelling species). Among these, the leafdwelling species are unique in building a sheet that lacks the tangle of lines above, and that is at one point connected to the underside of a leaf where the spider rests closely attached to the leaf surface ( Figs 8, 15, 16 View Figures 5–16 ). Modisimus vittatus seems to be the only species that tolerates (or prefers) considerable aridity, and that is thus found in city gardens, in exposed road embankments, and even among cacti and agaves in semi-arid scrubland.

Amber species: The results of our analyses using X-ray computed tomography were severely limited by low contrast for most specimens. This probably results from precipitations that often replace the original amber inclusion, and that negatively affect the contrast, thereby resulting in uneven surfaces. Major morphological characteristics were still partly visible, like humps on the chelicerae or palpal apophyses, but small relevant details like modified hairs on the chelicerae, or the morphology of the procursus, could not be resolved.

Our comparison of amber species with extant species is thus largely limited to characters that have either been described in the original publication ( Wunderlich, 1988), or that can be observed with a light microscope. All amber species described seem to be close to, or part of, the femoratus group. They are all long-legged species, with a rather high ocular area (unlike the fuscus group), they all seem to have a dorsal process on the procursus (unlike the southern paleoisland group; however, in M. oculatus this cannot be seen clearly), and they all seem to have AMEs (unlike the leaf dwellers; not visible in M. tuberosus ).

Other characters support this conclusion, but are not clearly visible in all species. The cheliceral armature of M. oculatus seems very close to that of M. femoratus and M. angulatus sp. nov. (frontal hump with stronger hairs). In M. calcar and M. calcaroides the cheliceral apophyses are more prominent (more like in M. jima sp. nov.), and at least in M. calcaroides they are also provided with stronger hairs. In M. tuberosus , the cheliceral prominence is again similar to M. femoratus , but is more conical; modified hairs might be present, but could not be seen. The abdomens of M. crassifemoralis and M. calcaroides are very similar to that of M. femoratus (slightly elongated and pointed at the spinnerets). The sternum of M. calcar is laterally brown, and lighter medially (unlike the southern paleoisland group and the leafdwelling species).

The exact origin is not known for any of the amber specimens. However, Dominican amber has only been found in the Cordillera Septentrional and the Cordillera Oriental of the northern and northeastern Dominican Republic ( Poinar, 1992). It is noteworthy that this coincides closely with a large part of the present-day distribution of the femoratus group. Apparently, the pholcids living in the northern Dominican Republic 15–20 Mya (Iturralde- Vinent & MacPhee, 1996) were not only congeneric with extant Hispaniolan species, but were even representatives of the same species group that today continues to dominate this area of the island. Alternatively, we cannot exclude the possibility that the resins are much younger. Ether tests, and the fact that the resins smear when ground, suggest that all specimens, except for M. calcaroides , might be preserved in copal rather than amber (J. Rust, pers. comm.).

MNHN

Museum National d'Histoire Naturelle

ZFMK

Zoologisches Forschungsmuseum Alexander Koenig

AMNH

American Museum of Natural History

Kingdom

Animalia

Phylum

Arthropoda

Class

Arachnida

Order

Araneae

Family

Pholcidae