Phylogeny and a new species of the enigmatic, troglobtic genus Alacran

There are many fantastic scorpions in the world, but among the more special are those being true troglobites showing special adaptions to a life in deep caves.The endemic genus of Mexico, Alacran Francke, 1982 (Typhlochactidae) is one of these special scorpions, only being found in deep caves.

Carlos Santibanez-Lopez and co-workers have now published a phylogenetic analysis of this remarkable genus and have also discovered a new species from the Tres Quimeras cave, in the
state of Puebla, south-eastern Mexico.

Alacran triquimera Santibanez-Lopez, Francke & Prendini, 2014

The three member of Alacran inhabit three isolated caves or cave systems. The article discuss how this distribution has originated.

A identification key for the genus is included.

Abstract:
The scorpion genus Alacran Francke, 1982, endemic to eastern Mexico, was created to accommodate Alacran tartarus Francke, 1982. This remarkable troglobiotic species is adapted for life in some of the world’s deepest caves, 720–916 m below the surface in the Sistema Huautla of the state of Oaxaca (the deepest records at which a scorpion has been found). A second species, Alacran chamuco Francke, 2009, was later described from Te Cimutaá, also in Oaxaca. In the present contribution,we describe a third species, Alacran triquimera, sp. nov., recently discovered in a cave system in the state of Puebla, and test the monophyly and internal relationships of Alacran, based on a cladistic analysis of 10 terminal taxa (including seven species representing all four genera of Typhlochactidae) and 151 informative morphological characters, building on a previously published matrix. The single most parsimonious tree obtained, supports the monophyly of Alacran and the following relationships among its component species: (A. chamuco (A. tartarus + A. triquimera, sp. nov.)). The phylogenetic relationships among the three species of Alacran are consistent with the biogeographical history of the caves they inhabit. Based on the geological history of the Sierra Madre del Sur and the likely similar speleogenesis of the Tres Quimeras, Sistema Huautla and Te Cimutaá caves, we propose a vicariance hypothesis to account for the disjunct distribution of the three species of Alacran, whereby an initially more widespread, panmictic ancestral population speciated into thre geographically isolated taxa following fragmentation of the southern Sierra Madre del Sur.

Reference:
Santibanez Lopez C, Francke OF, Prendini L. Shining a light into the world’s deepest caves: phylogenetic systematics of the troglobiotic scorpion genus Alacran Francke, 1982 (Typhlochactidae : Alacraninae). Invertebrate Systematics. 2014;28:643-64. [Subscription required for full text]

Thanks to Carlos Santibantez-Lopez for sending me this article!

Family Typhlochactidae

Robert W. Mitchell - RIP

I'm sorry to announce the recent death of the cave biologist and invertebrate zoologist Robert W. Mitchell (1933-2010). Dr. Mitchell has a very long and impressive list of publications, but for us scorpion people he is especially known for his work on troglobitic and troglomorphic scorpions.

Scorpion taxa described by Dr. Mitchell:

Typhlochactas Mitchell, 1971
T. reddelli Mitchell, 1968
T. rhodesi Mitchell, 1968
Sotanochactas elliotti (Mitchell, 1971)

Typhlochactas mitchelli Sissom, 1988 was named in honor of Dr. Mitchell.

In the early days of The Scorpion Files (2001-2002), Dr. Mitchell contacted me and sent me several pictures of some of "his" troglobitic scorpions to be used in The Scorpion Files. This was a great gesture, as these scorpions are among the rarest scorpions in the world, and I'm very grateful for his contribution!

RIP!

The Scorpion Files Gallery

The evolution of troglobitism and more on typhlochactid phylogeny

Recently, there have been several papers published on the troglomorphic scorpions of North America (see recent blog postings). Prendini, Francke & Vignoli have now published an article that focus on the evolution of troglobitic and troglomorphic scorpions and discuss if troglobitism can be considered an evolutionary dead-end. The paper also take a look at typhlochactid trichobothriotaxy and phylogeny.

A summary of the paper can be found below, but it is interesting to note that the authors conclude that troglobitism is not an evolutionary dead-end: that an ancestral troglobitic condition can evolve into a troglomorphic, endogean (above surface) condition. The authors belive that this is the case for the troglomorphic, litter dwelling species of Typhlochactas. In plain text: Specialized, troglobitic cave dwelling scorpions can go back to the surface and during evolution evolve into new species adapted to a more variable and demanding environment. So troglobitism is not necessarly an evolutionary dead-end.

Abstract:
The scorpion family Typhlochactidae Mitchell, 1971 is endemic to eastern Mexico and exclusively troglomorphic. Six of the nine species in the family are hypogean (troglobitic), morphologically specialized for life in the cave environment, whereas three are endogean (humicolous) and comparably less specialized. The family therefore provides a model for testing the hypotheses that ecological specialists (stenotopes) evolve from generalist ancestors (eurytopes) and that specialization (in this case to the cavernicolous habitat) is an irreversible, evolutionary dead-end that ultimately leads to extinction. Due to their cryptic ecology, inaccessible habitat, and apparently low population density, Typhlochactidae are very poorly known. The monophyly of these troglomorphic scorpions has never been rigorously tested, nor has their phylogeny been investigated in a quantitative analysis. We test and confirm their monophyly with a cladistic analysis of 195 morphological characters (142 phylogenetically informative), the first for a group of scorpions in which primary homology of pedipalp trichobothria was determined strictly according to topographical identity (the ‘‘placeholder approach’’). The phylogeny of Typhlochactidae challenges the conventional wisdom that ecological specialization (stenotopy) is unidirectional and irreversible, falsifying Cope's Law of the unspecialized and Dollo's Law of evolutionary irreversibility. Troglobitism is not an evolutionary dead-end: endogean scorpions evolved from hypogean ancestors on more than one occasion.

Reference:
Prendini L, Francke OF, Vignoli V. Troglomorphism, trichobothriotaxy and typhlochactid phylogeny (Scorpiones, Chactoidea): more evidence that troglobitism is not an evolutionary dead-end. Cladistics. 2010;26(2):117-142. [Subscription required for full text]

Thanks to Oscar Francke for sending me this paper!

Family Typhlochactidae

Major revision of troglomorphic North American scorpions results in a new family and genus

The fantastic troglomorphic and trglobitic scorpions of Mexico have been placed in different families since their discovery. The study of these enigmatic scorpions has been difficult because of their cryptic ecology (some species living deep in narrow caves) and low population numbers. Only 29 specimens have been collected in the last 40 years. The species has until recently been placed in the family Superstitioniidae.

In a recent revision of all known specimens, Valerio Vignoli & Lorenzo Prendini (2009) have redescribed all species and conducted a cladistic analysis. This has resulted in the elevation of the old family Typhlochactidae Mitchell, 1971. In addition, the new genus Stygochactas Vignoli & Prendini, 2009 has been created to accomodate the species S. granulosus (Sissom & Cokendolpher, 1998), previously placed in Typhlochactas Mitchell, 1971.

The following taxa have been transfered from Superstitioniidae to Typhlochactidae:

Alacran tartarus Francke, 1982
Alacran chamuco Francke, 2009 (not in this paper, but published a few weeks ago)
Sotanochactas elliotti (Mitchell, 1971)
Stygochactas granulosus (Sissom & Cokendolpher, 1998)
Typhlochactas cavicola Francke, 1986
Typhlochactas mitchelli Sissom, 1988
Typhlochactas reddelli Mitchell, 1968
Typhlochactas rhodesi Mitchell, 1968
Typhlochactas sissomi Francke et al., 2009
Typhlochactas sylvestris Mitchell & Peck, 1977

Abstract:
The scorpion family Typhlochactidae Mitchell, 1971, endemic to eastern Mexico, comprises nine troglomorphic species specialized for life in hypogean and endogean habitats. Due to their cryptic ecology, inaccessible habitat, and apparently low population density, Typhlochactidae are poorly known. Only 29 specimens have been collected in 40 years. Four species are known from a single specimen, two species are known only from the male and three only from the female. We provide an illustrated revision of the family based on a reexamination of most specimens in the world’s collections, including new specimens collected after the original descriptions and older specimens not previously described. Based on results of a recent cladistic analysis, Typhlochactidae are elevated, for the first time, from their former rank as subfamily, first of Chactidae and, more recently, of Superstitioniidae. Alacraninae, new subfamily is created to accommodate Alacran Francke, 1982. Stygochactas, new genus, is created to accommodate Typhlochactas granulosus Sissom and Cokendolpher, 1998 in a new combination. Sotanochactas Francke, 1986, Stygochactas and Typhlochactas Mitchell, 1971 are retained in subfamily Typhlochactinae Mitchell, 1971. Diagnoses of the family and subfamilies are presented, followed by a key to the genera and species, revised diagnoses of the genera, revised diagnoses and descriptions, tabulated meristic data, and distribution maps of the species. Descriptions and diagnoses are illustrated with ultraviolet fluorescence and visible light photographs, providing a visual atlas to the morphology of these remarkable scorpions. A review of their taxonomic history is provided, the importance of trichobothriotaxy for their systematics discussed, and several misconceptions in the literature clarified.

Reference:
Vignoli V, Prendini L. Systematic revision of the troglomorphic North American scorpion family Typhlochactidae (Scorpiones, Chactoidea). Bulletin of the American Museum of Natural History. 2009; (326):1-94. [Free fulltext]

Family Typhlochactidae

A new cave scorpion from Mexico

Mexico has many deep cave system and in these system there are some fantastic troglobitic scorpions (lacking eyes and pigmentation). Oscar Francke has now described a new species in the genus Aalcran from a cave in Oaxaca, Mexico. This is the seccond species in this genus. The other species (A. tartarus Francke, 1982) is only known from a handful of specimens.

Alacran is currently placed in the family Superstitionidae, but according to the information in Francke's paper a forthcomming paper by Vignoli & Prendini will reinstate the family Typhlochactidae Mitchell, 1971 for Alcran and probably other similar genera in the family Superstitionidae. I will blog details about this as soon as I have access to the paper and it's formally published.

Alacran chamuco Francke, 2009 (Superstitionidae/Typhlochactidae)

Abstract:
Alacran chamuco sp. nov., a new eyeless, troglobitic scorpion from Te Cimutaa, Valle Nacional, is described. This is the second known species in the genus; sharing with Alacran tartarus a very similar trichobothrial pattern and the lack of “petite” trichobothria—both unique characters in the family Typhlochactidae. The new species differs from A. tartarus in the pedipalp finger dentition and the relative size of the telson. The two cave systems in Oaxaca where the two species of Alacran occur are approximately 75 kilometers apart.

Reference:
Francke OF. A new species of Alacran (Scorpiones: Typhlochactidae) from a cave in Oaxaca, Mexico. Zootaxa. 2009; (2222):46-56. [Subscription required for fulltext]

Thanks to Dr. Jean-Michel Pacaud for sending me the Francke paper!

Family Superstitionidae