Great Basin Naturalist Memoirs Volume 7 Biology of Desert Rodents Article 2 8-1-1983 Evolutionary relationships of heteromyid rodents John C. Hafner Moore Laboratory of Zoology and Department of Biology, Occidental College, Los Angeles, California 90041 Mark S. Hafner Museum of Zoology and Department of Zoology and Physiology, Louisiana State University, Baton Rouge, Louisiana 70893-3216 Follow this and additional works at: https://scholarsarchive.byu.edu/gbnm Recommended Citation Hafner, John C. and Hafner, Mark S. (1983) "Evolutionary relationships of heteromyid rodents," Great Basin Naturalist Memoirs: Vol. 7 , Article 2. Available at: https://scholarsarchive.byu.edu/gbnm/vol7/iss1/2 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist Memoirs by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. EVOLUTIONARY RELATIONSHIPS OF HETEROMYID RODENTS' John C. Hafner and Mark S. Hafner' Abstract.— The rodent superfamily Geomyoidea is an old, undoubtedly inonophyletic lineage having only ob- scaire affinities with other rodent groups. Geomyoid rodents, autochthonous in North America, experienced major evolutionary diversification in the Mio-Pliocene coincident with the development of the Madro-Tertiary Geoflora and the climatic trend toward increasing aridity and coolness. Extant geomyoids are divisible into two groups: (1) the Geomyidae, all members of which are fossorial, and (2) the Heteromyidae, whose members display an adaptive con- tinuum from bipedal, xeric-adapted forms to scansorial, mesic-adapted forms. These moieties, although recognizable on biochemical criteria, become particularly difficult to distinguish when paleontological data are considered. Nev- ertheless, most lines of evidence indicate that the families Heteromyidae and Geomyidae are distinct, monophyletic lineages. The extant heteromyids comprise three main lineages (including six genera) that diverged during the Eocene: (1) subfamily Perognathinae (Chaetodipus and Perognathus); (2) subfamily Dipodomyinae (Dipodoinys and Micro- dipodiips); and (.3) subfamily Heteromyinae {Lioimjs and Heteromijs). Protein differentiation has occurred at hetero- geneous rates among these major lineages. Based on available karyotypic data, the main direction of chromosomal evolution in the Heteromyidae appears to be toward increasing chromosome number. Cladistic analysis of morpho- logical characters used in previous studies supports biochemical evidence allying Microdipodops with Dipodoinys. A model is introduced to describe how heterochronic changes in ontogeny may explain the great breadth of morpho- logical diversification within the superfamily. Taxonomic recommendations at the subfamilial, generic, and sub- generic levels are provided. The most important point to be emphasized is that relationships within the Heteromyidae was "Parallelism, parallelism, more parallelism and still Wood's exhaustive treatment, now aged one- more parallelism" is the evolutionary motto of the ro- half century. However, during the past 50 dents in general and of the heteromyids in particular. volume of literature per- This extends to all parts of the body. It makes the task of years a tremendous determining interrelationships particularly difficult, and taining to heteromyid evolution has accumu- renders exceptionally dangerous any postulates as to lated, justly reflecting the immense interest what the relationships of a given form may really be, if in these mammals. Some of the questions hill evidence does not exist to clear the maze of parallel posed by Wood and the others have been an- adaptations for us. This shows the insuperable diffi- culties awaiting anyone who attempts a classification swered to satisfaction, whereas the answers to based on a single character or on a group of characters other queries still elude us and await extrica- with a common cause. tion by future research. Albert Elmer Wood (19.35:250) It is the intent of this contribution to pre- A trio of monographs on the evolutionary sent a compendium of the evolution of heter- biology of heteromyid rodents appeared in omyid rodents, wherein we attempt to in- the early 1930s and, subsequently, has hall- tegrate the classic morphological studies of marked this specialized area of scientific in- the 1930s with the more recent systematic quiry. Hatt (1932) and Howell (1932) pro- treatments. As a definitive statement on het- vided definitive accounts of the morphology eromyid relationships, this effort may appear of the ricochetal forms, and Wood (1935) inchoate in a few years. However, the assimi- synthesized the then available data, gleaned lation of earlier ideas with those of the pres- is neces- from fossil and recent forms, into a coherent ent, coupled with due introspection, of summarization. Interestingly, the last com- sary in any field of science. The study prehensive statement of the evolutionary heteromyid evolution is no exception and of Mammalogists, hosted by Brigham Young 'From the symposium "Biology of Desert Rodents," presented at the annual meeting of the American Society University, 20-24 June 1982, at Snowbird, Utah. 90041. 'Moore Laboratory of Zoology and Department of Biology, Occidental College, Los Angeles, California Louisiana 70893-3216. •Museum of Zoology and Department of Zoology and Physiology, Louisiana State University, Baton Rouge, Great Basin Naturalist Memoirs No. 7 through this reflection of the present to the myoids, and it was not mitil 1848 that Water- past we hope to gain a profitable avenue for house recognized the Saccomyina ( = modern further investigations. Geomyoidea) as a distinct group of New The evolution of the Heteromyidae (kan- World rodents (Waterhouse 1848). In 1872, garoo rats, pocket mice, and their allies) is Gill recognized two closely related families closely associated with that of the Geo- within Waterhouse's Saccomyina, the Geo- myidae (pocket gophers) and, consequently, myidae ( = modern Geomyidae) and the Sac- tlieir taxonomic histories are necessarily in- comyidae (= modem Heteromyidae). Gill tertwined. Together these two families form (1872) imited these families under the super- an internally cohesive superfamily (the Geo- familial nomen, Saccomyoidea. Weber myoidea) whose members are miited by the (1904), recognizing that Saccomys Cuvier presence of externally opening, fur-lined 1823 was a junior synonym of Heteromys cheek pouches (among other features). Geo- Desmarest 1817 (see Gray, 1868 for details), myoid rodents underwent major phyletic first used the superfamily name Geomyoidea. radiation from the Oligocene to Pliocene of The phyletic position of the Geomyoidea North America, in step with the global trend within the order Rodentia has long been a toward a cooler and drier climate (Flint matter of debate. Coues (1877) considered 1971) and the diversification and migration the geomyoids to be "myomorphs" {sensii of geofloras (Axelrod 1950, 1958, 1976). His- Brandt, 1855). However, Miller and Gidley toric biogeographic considerations have been (1918) and many recent workers place the presented elsewhere (e.g.. Wood 1935, geomyoids near, or within, the "sci- uromorphs" (e.g., Simpson, Most Reeder 1956, Genoways 1973, Hafner, J. C., 1931, 1945). 1981a) and will not be repeated here; for recently. Wood (1965:128) suggested that the general reviews see Stebbins (1981; coe volu- muroid and geomyoid rodents may have tion of grasses and herbivores), and Cole and shared a common ancestor within the primi- Armentrout (1979; Neogene paleogeog- tive, protrogomorphous rodent family Sciura- raphy). It is interesting to note, however, that vidae, and he thus placed the Geomyoidea heteromyids and geomyids represent two of within the suborder Myomorpha (see also the three families of living mammals autoch- Wood 1955, Wahlert 1978). thonous in continental North America (the Rodents of the family Eomyidae represent third being Antilocapridae). As a con- a third, wholly extinct group of geomyoid ro- sequence of the similarities in heteromyid dents present from late Eocene to Plio- and geomyid biogeographic histories and Pleistocene in Europe and North America. their intimate phyletic relationships, we have According to Wilson (1949a, 1949b), who found it illuminating to include relevant geo- first placed the eomyids within the Geo- myid information in this review of the Heter- myoidea, the eomyid skull shows many sim- omyidae. Indeed, in order to appreciate fully ilarities to both primitive heteromyids and the history of evolutionary diversification cricetids. Wood (1955) concurs with Wilson within the Heteromyidae, it is necessary first in recognizing the Eomyidae as a primitive to view this family within the broader frame- geomyoid group, perhaps ancestral to the work of the superfamily Geomyoidea. Heteromyidae. However, none of the known eomyid forms appears to be directly ancestral Review of Geomyoid Systematics to living geomyids or heteromyids (Wahlert 1978). The taxonomic history of the Geomyoidea The phyletic propinquity of geomyids and began with the description of the "tucan" or heteromyids, and the fact that both groups "Indian mole" (probably a pocket gopher, evolved imder similar environmental condi- Tliomomys) by Fernandez in 1651. According tions in western North America, may account to Merriam (1895:201), both Fernandez and, for the remarkable