II - About Salticidae

Biological background of taxonomic decisions

Good taxonomic work should have biological meaning, otherwise its value is comparable to collecting postage stamps. The routine practice of taxonomy seldom allows time for direct biological research, but nonetheless the biology of the animal should always be in the mind of a taxonomist. Species theory (based on the ideas of Ernst Mayr) holds that every species comprises one or more populations which, in normal environmental conditions, share a common gene pool and are potentially capable of interbreeding, irrespective of how variable they appear to be. The description of a new species is a hypothesis that the described specimens derive from a unique population, separated from other species by a genetic gap.

Species differ by morphological characters, biological properties, history and geographical areas of distribution. The decision on splitting or lumping previously described species should be taken with consideration of the biological properties of the species. Subspecies are local populations of a species, sharing at least 75% of characters with other populations of the same species, and potentially interbreeding with them. So distinguishing a subspecies requires ecological and other biological research, normally not available to a taxonomist working on preserved collections.

Subspecies described in Salticidae are, with rare exceptions, either specimens of variable species, or represent different species which a taxonomist hesitated to describe. The majority of subspecies described in the Salticidae can therefore be dismissed.

Genus. Species originate by a process of speciation, in Salticidae probably exlusively by geographical speciation. Related species form a clade, sharing some characters and properties, and in time these may differentiate to become more distinct. Evolution of various characters seems not to be correlated within the Salticidae, and no single character is sufficient to define clades. The evolution of some characters is linear within particular clades, but may occur in parallel in unrelated clades. Some of the most reliable characters, (e.g. channels in the internal structure of the epigyne, or embolus length which evolve from short ones, gradually lengthening and then becoming twisted into coils or spirals) could very well be used for defining species within a clade, but are misleading when one searches for relationships among clades. There are no objective criteria for defining which species should be included in a particular genus, a taxonomist decides subjectively whether a single clade should be described as a single genus, or split into a number of genera, sometimes even naming each species as a separate genus (as has happened in the taxonomy of bears). Vanity prompts many taxonomists to become Authors of new genera (or even new subfamilies), which leads to a devaluation of genera and obscures their interrelationships. While there are no criteria for the delimitation of genera, nonetheless there are ‘good’ genera, and ‘poor’ genera. A good genus corresponds with a clade and all species in it are related. It facilitates storage of information, and their retrieval. A common sin of taxonomists is inventing new names and shifting species between genera without any real necessity and with insufficient documentation. Species should not be renamed solely on the basis of a discovered homonym (as often happens in Catalogues) - such cases should be pointed out, but should be delayed until the next taxonomic revision of the species in question.
An example of bad service to taxonomy is the dispute on name Chira (search under "C" in Catalogues) versus Shira (search under "S" in Catalogues). Recognition of clades implies that it is not important to decide whether two forms belong to a single species, or to two subspecies, or to sibling species: the important point is to recognize that the two forms are closely related. Examples are the trans-Atlantic forms Sitticus floricola and Sitticus palustris, or Evarcha falcata and E. hoyi.
Such disputes can be solved only by breeding experiments and perhaps also by gene sequencing, which has not as yet been attempted.

Provisional classification of genera and subfamilies of Salticidae

The natural classification of more than 6,000 species of Salticidae has great importance in synthesizing information on these spiders and developing ways of species identification, all over the globe. The search for a concensus for delimiting the subfamilies has been ongoing for over 100 years, but a significant break through seems to occurred only now, with the new technique of gene sequencing (Maddison & Hedin, 2003, Maddison & Zhang, 2006, Maddison, Zhang & Needham, 2007, Maddison, Bodner & Needham, 2008), which has produced a phylogenetic tree proposing relationships between various taxa. The summary of major clades distribution over continents and remarks on the problems of Salticidae classification, given in the latter papers of 2003 and 2008 (see copies below) are particularly enlighting and instructive.

The display of genera grouped into subfamilies and two higher categories in this database facilitates technical means of comparison of  morphological genitalic characters with results of gene sequencing research, published to date. The display is provisional, because both types of data are preliminary: gene sequencing is too new to evaluate them, whereas on the other hand genitalic characters are very incomplete: in spite of more than 100 years of study only 4041 species (out of some 6,000 in the data base) seem to have diagnostic drawings of any kind (often utterly valueless). Still, comparison of gene sequencing data with traditional documentation seems to offer a potential means towards a deeper understanding of Salticid taxonomy and systematics .


Originally, the extensive classification of Salticidae was presented by Simon (1902-1903), who divided the family into 69 groups of genera, of roughly homogenous external appearance. These groups are still influencing taxonomic thinking today,  although the contents of some groups, and the relationships between them, are no longer acceptable. Simon’s methodology is illustrated in the diagram of 22 subfamilies, compiled by Petrunkewith, 1928. A summary of Simon’s group was listed by Bonnet, 1959: 5052-5054, Roewer, 1954 has arranged the genera by subfamilies in his “Katalog” (with a rather inconvenient result).

Inadequacies of Simon’s methodology were demonstrated by Prószyński, 1972 (see diagram above), who proposed an entirely different approach, concentrating on standardized drawings of palps and internal structures of epigynes. That approach has failed to produce a usable phylogeny of the family, as often happens with one-sided analyses, but created extensive genitalic taxonomic data (Prószyński 1966, 1968a, 1968b, 1968c, 1976, 1984a, 1984b, 19843c, 1985a, 1987 and remaining papers by Prószyński). Diagnostic genitalic drawings were also used by Galiano (all papers from 1957 untill 2001) and became standard taxonomic documentation in the world’s Salticidae literature. Documentation of palps and epigynes (although usually not the internal structure of the epigyne) were used regularly for defining species in a number of papers, beginning from Peckham & Peckham (1883-1909), Kulczyński (1884-1911), and for selected species  in numerous papers during the twentieth century, often diagrammatized and often of little value. However, these were not used for defining phylogenetic relationships.
Disclaimer. Names of  categories above the genus level in the "Search a taxon" display are not intended as proposals for taxa – but serve as provisional intermediary links between genera, subfamilies, groups of subfamilies and infra-families, necessary for the correct functioning of the display. The database requires that no field  be left blank, so I had to invent provisional and informal interconnecting names for the fields lacking formal names, some of these are marked by endings -es, -s. I do not consider the usage of such interconnecting names in this database as a formal proposal to create them, in a sense of the ICZN, and stipulate that they will be replaced in the future by formally described names. J. Prószyński, 2011.Some additions
Grupa Diolenieae Simon was raised to subfamily by Gardzinska J. 2004 [ Rewizja taksonomiczna grupy Dioleniae (Araneae: Salticidae). PhD Thesis in Akademia Podlaska, Siedlce 1-162, illustrations plates 1-77]. Some parts of that paper were published in Gardzinska J. 2006 [ A revision of the spider genus Ohilimia Strand, 1911 (Araneae: Salticidae). Annales zoologici, Warszawa 56(2): 375-385, illustrations 1-48], Gardzinska J., Zabka M. 2005. [A revision of the spider genus Chalcolecta Simon 1884 (Araneae: Salticidae). Annales zoologici, Warszawa 55: 437-448, illustrations 1-59] and Gardzinska J., Zabka M. 2006 [ A revision of the spider genus Diolenius Thorell, 1870 (Araneae: Salticidae). Annales zoologici, Warszawa 56(2): 387-433, illustrations 1-217].

Interpretation of geographical distribution and phyletic relationships
(the chapter under construction)

 Faunal study of Salticidae of Europe, gives little material to phyletic considerations, due to non-homogenous contents of not related post-glacial immigrants, and less numerous pre-glacial survivors. Traces of evolution are better visible in geographical areas with long history of environments, especially located in warm climate, and diversified, but numerous dispersion barriers (physical, ecological, etc.). Speciation processes were particularly intensive in centers of origin, and centers of secondary dispersion – such as mountains in tropical climate and islands archipelagoes. Species spread from centers into neighboring areas, with intensity differentiated by ecological valence of species: some spread only over small areas, other dispersed over large distances, many died with time.
The above is the general picture I have formed for myself from general theories of species and dynamic zoogeography. To that I added preliminary
conclusions from taxonomic studies I carried in 1960ties-1980ties on particular genera (Sitticus, Yllenus, Phintella, Pseudicius, Telamonia, and other).
The sketches below are hypotheses, which I will not be able to develop further.  

An example of hypothesis explaining origin of geographical ranges of three congeneric, but not directly sibling, species of Evarcha, is presented on the diagram below. .  

Interesting result of faunal studies is possibility of deciphering history of a genus from its present day geographical distribution, correlated with morphological hints of affinities. Lack of parameter of time could be compensated to some extent by comparison of faunae of environments of known age. However, such interpretations are limited to certain span of time and the picture of history could change diametrally with new data. An example of such change begins with summary of taxonomic revisions of Sitticus (Prószyński 1983), allowing hypothesis that the genus has apparently developed in the Palaearctics, sending immigrants to North America several times: at the relatively earliest period (resemblance of the relict S. longipes to S. absolutus), during existence of Bering land bridge (S. ranieri), in the XIXth-XXth century, and precisely dated arrival of S. niveosignatus in 1958. There were also some returns back of American species into Palaearctics (S. cutleri). Origin of S. rupicola could be related to one of interglacial episodes. That nice picture has been turned upside down by phyletic studies (Maddison, Hedin, 2003) placing, Sitticus inside Neotropical group of subfamilies Amycoida. So it could be understood now that Sitticus originated in S America, dispersed to North America, some species migrated futher to Palaearctics, as testified by relict S. longipes. The remaining part of hypothesis – further development in Palaearctics and several migrations to N America could be accepted, at least for the time being.

 

 

 

 

 

Prószyński, 2011.