Article

THE RIPARIANNESS OF A DESERT HERPETOFAUNA1

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

Within the Mojave, Sonoran, and Chihuahuan Desert subdivisions of the North American Desert in the U.S., more than half of 143 total amphibian and rep- tilian species perform as riparian and/or wetland taxa. For the reptiles, but not the amphibians, there is a sig- nificant inverse relationship between riparianness (obli- gate through preferential and facultative to nonriparian) and desertness. In addition to the nondesert species (N=36) present, there are two evolutionary kinds of desert species in the herpetofauna: true desert species (N-20), and desert-included species (N=87); the former are obligate specialists, the latter are facultative gener- alists. Quantitative aspects of desertness, riparianness, species richness, nondesert taxa and others are exam- ined. A large part of the herpetofauna of North America is located extensively and abundantly in riparian habitats. No other terrestrial vertebrate group is a better indicator of the biological health of riparian ecosystems. Within the "warm deserts" of the Southwest United States more than half of the total amphibian and reptilian species perform as riparian and/or wetland taxa. Riparian taxa are obligate, preferential, or facultative components of riparian ecosystems. Thus including the nonriparian condition, four levels of riparianness (R), or riparian dependency, are recognized (Dick-Peddie and Hubbard 1977, Johnson, and others 1987). Moreover, for deserts, in addition to the distinction between desert species and nondesert species, there is a clear distinction between two evolutionary kinds of desert species: true desert species and desert-included species. True desert species are obligate specialists in the real sense that they have evolved within desert environments, while the desert- included species tend to be facultative generalists that include desert environments in their much wider and often widely extensive ecological and geographical distributions. Thus including the nondesert condition, three levels of desertness (D) are recognized (Lowe 1968; and others, 1986):

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... Our approach is applicable across taxa from various riparian systems, though we focused on reptiles and amphibians. In the arid southwest of the U.S., more than half of all species of reptiles and amphibians utilize riparian or wetland habitats (Lowe, 1989) even though riparian vegetation comprises less than 1% of the landscape (Knopf et al., 1988;Knopf and Samson, 1994). However, it is predicted that freshwater resources in this region will experience further stresses over the coming decades and that climate change will shift patterns of aridity and precipitation (IPCC, 2007). ...
Article
Full-text available
Altering stream flows and groundwater have modified how streams are connected to riparian floodplain vegetation. This disconnection has led to the proliferation of non-native and invasive woody plant species and altered habitat complexity. Squamate vertebrates such as lizards and snakes, and amphibians such as frogs and toads, are important food web links in riparian ecosystems of the Sonoran Desert. We explored the relationship between habitat heterogeneity and species diversity in aridland riparian ecosystems in the United States (US). Specifically, we measured riparian vegetation composition, cover, and habitat structure from the Middle Rio Grande in New Mexico, the San Pedro and Gila Rivers in Arizona, and the Virgin River in Nevada. We used pitfall arrays deployed in these riparian forests to document reptile and amphibian communities. We developed a habitat index by weighing variables based on their contributions to variation explained in the dataset and characterized the structural attributes and heterogeneity of the riparian vegetation. We validated the habitat index by relating it to abundance and richness of reptile and amphibian species and found a positive relationship. Native riparian trees and stands mixed with native and non-native trees supported greater diversity and abundance of lizard fauna compared to monotypic stands of non-native trees. We integrated elements of vegetation structure and composition with ectothermic wildlife to show how riparian areas provide complex habitat for species. Our results suggest that riparian woodlands provide higher quality habitat for riparian reptile and amphibians compared to non-native stands.
... These attributes will allow Russian olive to persist and further expand its range on regulated and unregulated rivers in the Southwest even under continued warming and drying, whereas native plant species will likely suffer. Because most wildlife in the arid Southwest rely on riparian habitat at some point in their annual cycle for food or shelter (Grinnell, 1914;Lowe, 1989;Rosenberg et al., 1991), Russian olive establishment is a legitimate concern for Southwest fauna. ...
Article
The establishment and naturalization of non-native Russian olive (Elaeagnus angustifolia) in southwestern US riparian habitats is hypothesized to have negative implications for native flora and fauna. Despite the potential for Russian olive establishment in new riparian habitats, much of its ecology remains unclear. Arid river systems are important stopover sites and breeding grounds for birds, including some endangered species, and understanding how birds use Russian olive habitats has important implications for effective non-native species management. We compared native bird use of sites that varied in the amount of Russian olive and mixed native/non-native vegetation along the San Juan River, UT, USA. From presence/absence surveys conducted in 2016during the breeding season, we found 1) fewer bird species and functional groups used Russian olive habitats and 2) the composition of species within Russian olive habitats was different from the composition of species in mixed native/non-native habitats. Our results suggest Russian olive may support different bird compositions during the breeding season and as Russian olive continues to naturalize, bird communities may change. Finally, we highlight the paucity of research surrounding Russian olive ecology and stress the need for rigorous studies to improve our understanding of Russian olive ecology.
... Globally, researchers have monitored responses of lizards to understand how habitat restoration affects animal populations, through changes in canopy of woody vegetation, ground litter structure, and microclimate, in grasslands (Steidl et al. 2013; Stellatelli et al. 2013), agriculture areas (Jellinek et al. 2014), and riparian areas (Bateman et al. 2008a). About 60% of amphibian and reptile species (collectively called herpetofauna) in the Chihuahuan, Great Basin, Mojave, and Sonoran Deserts of North America utilize riparian or wetland habitats (Lowe 1989). ...
Article
Full-text available
Amphibians and reptiles (herpetofauna) have been linked to specific microhabitat characteristics, microclimates, and water resources in riparian forests. Our objective was to relate variation in herpetofauna abundance to changes in habitat caused by a beetle used for Tamarix biocontrol (Diorhabda carinulata; Coleoptera: Chrysomelidae) and riparian restoration. During 2013 and 2014, we measured vegetation and monitored herpetofauna via trapping and visual encounter surveys (VES) at locations affected by biocontrol along the Virgin River in the Mojave Desert of the southwestern United States. Twenty-one sites were divided into four riparian stand types based on density and percent cover of dominant trees (Tamarix, Prosopis, Populus, and Salix) and presence or absence of restoration. Restoration activities consisted of mechanically removing non-native trees, transplanting native trees, and restoring hydrologic flows. Restored sites had three times more total lizard and eight times more yellow-backed spiny lizard (Sceloporus uniformis) captures than other stand types. Woodhouse's toad (Anaxyrus woodhousii) captures were greatest in unrestored and restored Tam-Pop/Sal sites. Results from VES indicated that herpetofauna abundance was greatest in the restored Tam-Pop/Sal site compared with the adjacent unrestored Tam-Pop/Sal site. Tam sites were characterized by having high Tamarix cover, percent canopy cover, and shade. Restored Tam-Pop/Sal sites were most similar in habitat to Tam-Pop/Sal sites. Two species of herpetofauna (spiny lizard and toad) were found to prefer habitat components characteristic of restored Tam-Pop/Sal sites. Restored sites likely supported higher abundances of these species because restoration activities reduced canopy cover, increased native tree density, and restored surface water.