Distribution, extent, and evolution of plant consumption by lizards

Abstract

Animal diets crucially affect ®tness, yet many aspects of their ultimate determinants are unknown. The distribution and extent of herbivory in lizards, its evolutionary history, and ecological factors that may favour it are discussed. Most lizards are exclusively or primarily carnivorous, yet many species eat some plants and a few are almost exclusively herbivorous. Based on a literature survey of diets of over 450 lizard species, the distribution and degree of omnivory and herbivory are described. Some plants occur in the diets of slightly over half of lizard species, and plants formed 10% or more of the dietary volume of 12.1% of species, and 90% or more of the diet of 0.8% of species. The greatest percentage of omnivorous species (> 10% plant diet), over 30% in each, and highest mean percentage plant matter in the diet are in Iguanidae, Corytophanidae, Gerrhosauridae, Agamidae, Xantusiidae, and Tropiduridae. Numerous other omnivores occur in Lacertidae and Scincidae and fewer in several additional families. Herbivorous lizards (> 90% plant volume) tend to be folivorous and to possess adaptations for processing leaves, including specialized dentition for cutting or reducing leaves, elongated intestines, colic valves that slow passage of food, and intestinal¯ora that digest cellulose. Omnivorous lizards lacking such specializations may eat some leaves, but consume much more fruit,¯owers, and seeds, plant parts that are easy to digest, likely to be very abundant seasonally, and may be highly nutritious. Some lizards eat nectar and pollen; even sap is eaten by at least one gecko. Ontogenetic increase in plant consumption and decrease in prey consumption is known, but its generality has been controversial. Such ontogeny has been demonstrated in three iguanid species, a skink, a lacertid, two tropidurids, a phrynosomatid, and two corytophanids, but it does not occur in some other species. Thus, the presences of ontogenetic variation must be evaluated for each species. The importance of speci®c foods may also vary with age. Omnivory and/or herbivory have originated in many lizard families, with at least nine origins in Iguania and 23 in Scleroglossa. Origins have been rare in Gekkonoidea and Anguimorpha and common in Scincomorpha, especially in Lacertidae and Scincidae. Losses of omnivory have been much less frequent than gains. Only a few origins can account for all the herbivory in lizards. Concentrated changes tests show that there is a signi®cant association in Lacertidae, Lacertiformes, Lacertoidea, Scincidae, and Scleroglossa between insularity and omnivory. Insular lizards may broaden their diets to compensate for limited availability of prey. Addition of other factors that reduce availability of prey, i.e. extreme aridity and cave-dwelling, to insularity, strengthened the relationship to omnivory in Lacertidae and Lacertoidea. We were unable to demonstrate a role of aridity independent of insularity, but present anecdotal evidence suggests that it may promote evolution of plant consumption. Large body size in...

Dietary-morphological relationships in fish assemblages of small forested streams in the Bolivian Amazon

“…These results accord, at least concerning invertivorous and piscivorous guilds, with the general observation that body and prey size are often correlated (Gatz 1979). The association between herbivory and large body size of species is difficult to interpret but has been also reported for other vertebrates such as lizards (Cooper and Vitt 2002).…”

Rigorous conditions for food-web intervality in high-dimensional trophic niche spaces

“…foraging traits of consumers that are located at or near the vulnerability traits of specific resources. The assumption of fast evolution of foraging traits is supported by empirical observations indicating that phylogenetic correlations among foraging traits are weak (Cooper and Vitt, 2002;Blomberg et al, 2003b;Bersier and Kehrli, 2008). In particular, taxonomically related resources tend to be preyed upon by similar consumers, while taxonomically related consumers to a lesser extend tend to prey on the same resources.…”

Temporal and Spatial Variation in the Diet of the Endemic Lizard Gallotia galloti in an Insular Mediterranean Scrubland

“…Therefore, one of the main tendencies of lizards in insular habitats, compared to mainland areas, is to include abundant plant matter in their diets (Pérez-Mellado and Corti, 1993;Van Damme, 1999;Cooper and Vitt, 2002;Olesen and Valido, 2003). High densities of lizards (Bennett and Gorman, 1979;Schoener and Schoener, 1980;Rodda and Dean-Bradley, 2002), lower arthropod prey availability (Janzen, 1973), larger body size (Szarski, 1962;Sokol, 1967;Pough, 1973;Herrel et al, 2004), lower predation risk (Szarski, 1962;Pérez-Mellado and Corti, 1993;Olesen and Valido, 2003), aridity, and foraging mode (Cooper and Vitt, 2002) has been suggested as the explanation of increase in plant material consumption on islands. However, Espinoza et al (2004) demonstrated that most herbivorous liolaemids are small bodied and live in cool climates.…”

“…During the dry period (summer), fleshy fruits supply an important amount of water (Pérez-Mellado et al, 1999). High consumption of fruits could be related to the dry conditions of this habitat during this season and the high water content of fruits (Jordano, 2000), as well as the overall availability of ripe fruits and maybe a decrease in invertebrate abundance as well (Cooper and Vitt, 2002;Olesen and Valido, 2003). Valido et al (2003) reported the frequent consumption of fleshy fruits by G. galloti throughout the year, reaching minimum values (FO , 30%) in the period December to February; a similar pattern was detected in our study.…”

“…In lacertids, plant consumption varies intraspecifically among seasons and populations (Cooper and Vitt, 2002;Perera et al, 2006). In the case of G. galloti, this has been reported among seasons and populations (Valido and Nogales, 2003).…”