Invasive fire ants alter behavior and morphology of native lizards (original) (raw)
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Canadian Journal of Zoology, 2009
The introduction of non-native species is becoming increasingly common. Understanding the impact of invaders on native populations is critical for effective management. Red imported fire ants (Solenopsis invicta Buren, 1972) were introduced to the USA in the 1930s. They will attack, and can kill, native fence lizards (Sceloporus undulatus (Bosc and Daudin in Sonnini and Latreille, 1801)), which co-occur with these ants across much of their invasive range. I determined whether fence lizards minimize encounters with S. invicta by altering their habitat use following invasion or avoiding cues of the presence of these fire ants. I recorded the habitat use of fence lizards and S. invicta mounds across four sites with different histories of invasion, and quantified lizard avoidance of S. invicta scent. I found that lizards do not alter their habitat use following S. invicta invasion, nor do they spatially avoid their mounds. Fence lizards do avoid S. invicta scent, but this was only evident in naïve or recently invaded populations. The lack of avoidance of S. invicta by fence lizards could be explained by the high prevalence of these fire ants, making them difficult to avoid, and adaptive shifts in the escape behaviour and morphology of these lizards following invasion that permit them to survive fire ant attack.
Wildlife Research, 2011
Context. Aggressive encounters, including those with venomous species, impose selective pressure on native species. Immediate lethal outcomes of these encounters have been the primary focus of research in this field. However, not all aggressive interactions result in immediate mortality, and indirect consequences of aggressive interactions may be an equally important but under-considered selective force. The red imported fire ant is a globally important venomous invader that imposes novel selective pressure on native communities.
Invader danger: lizards faced with novel predators exhibit an altered behavioral response to stress
Hormones and behavior, 2011
Animals respond to stressors by producing glucocorticoid stress hormones, such as corticosterone (CORT). CORT acts too slowly to trigger immediate behavioral responses to a threat, but can change longer-term behavior, facilitating an individual's survival to subsequent threats. To be adaptive, the nature of an animal's behavior following elevated CORT levels should be matched to the predominant threats that they face. Seeking refuge following a stressful encounter could be beneficial if the predominant predator is a visual hunter, but may prove detrimental when the predominant predator is able to enter these refuge sites. As a result, an individual's behavior when their CORT levels are high may differ among populations of a single species. Invasive species impose novel pressures on native populations, which may select for a shift in their behavior when CORT levels are high. We tested whether the presence of predatory invasive fire ants (Solenopsis invicta) at a site affects the behavioral response of native eastern fence lizards (Sceloporus undulatus) to elevated CORT levels. Lizards from an uninvaded site were more likely to hide when their CORT levels were experimentally elevated; a response that likely provides a survival advantage for lizards faced with native predatory threats (e.g. birds and snakes). Lizards from a fire ant invaded site showed the opposite response; spending more time moving and up on the basking log when their CORT levels were elevated. Use of the basking log likely reflects a refuge-seeking behavior, rather than thermoregulatory activity, as selected body temperatures were not affected by CORT. Fleeing off the ground may prove more effective than hiding for lizards that regularly encounter small, terrestrially-foraging fire ant predators. This study suggests that invasive species may alter the relationship between the physiological and behavioral stress response of native species.
Sublethal effects of invasive fire ant venom on a native lizard
Journal of Experimental Zoology …, 2010
Invasive species can impose novel selection pressures on natives, such as toxins to which native taxa are not adapted. Native species may survive such invasions by evolving mechanisms to avoid toxin exposure or increase toxin tolerance. Red imported fire ants (Solenopsis invicta) employ an alkaloid-based venom to defend their colonies and capture prey. In this study we aim to characterize the sublethal effects of invasive fire ant venom on a native vertebrate, the eastern fence lizard (Sceloporus undulatus), and to determine whether lizard populations that have been exposed to these fire ants for $35 generations have increased physiological resistance to the venom. We documented the sublethal impact of fire ant venom on fence lizard performance by naturally exposing lizards to fire ant stings and recording changes in three fitness-relevant measures: bite force, righting ability, and sprint speed. We also measured blood hemolysis induced by the venom. To test for the development of physiological resistance to fire ant venom we compared whole-body performance and hemolysis for two populations of lizards with different fire ant invasion histories. Fire ant venom showed no dosage-dependent sublethal effects on performance. In addition, there is no evidence that lizards have evolved increased physiological resistance: the impact of fire ant venom on whole-body performance and hemolysis did not differ between the naïve and experienced populations. Lizards may instead rely on adaptive shifts in escape behavior and morphology following invasion to survive fire ant attack.
Texas Horned Lizard Declines and the Invasive Red Fire Ant
The extirpation of the Texas Horned Lizard, Phrynosoma cornutum, from most counties in Texas is largely associated with the introduction and spread of the Red Fire Ant, Solenopsis invicta. An examination of the limiting factors in the spread of the ants help explain why the horned lizards still thrive in some locations.
Can behaviour explain invasion success? A comparison between sympatric invasive and native lizards
To reduce the impact of biological invasions, we need to understand the behavioural mechanisms that enable some species to be successful invaders. Testing differences in behaviour between sympatric congeneric species with different invasive potential is an opportunity to study specific behavioural traits associated with invasion success. Using the invasive Italian wall lizard, Podarcis sicula, and a noninvasive congeneric, the green Iberian wall lizard, Podarcis virescens, which live in sympatry in a location that is novel for P. sicula, we tested their exploratory behaviour, neophobia and boldness: all traits that should promote invasion success. The invasive P. sicula was more exploratory, bold and neophilic than the sympatric native P. virescens. Native lizards had highly repeatable behaviour, whereas in P. sicula boldness was the only behavioural trait that was repeatable. The behavioural traits of the native species, but not the invasive species, were correlated. A lack of correlation between behavioural traits, as well as a lack of repeatability in two of the three behavioural traits, suggests higher levels of behavioural plasticity in P. sicula, which may also explain the success of this lizard during invasions. Our experiment highlights the potential importance of behavioural traits in invasions and provides insight into why P. sicula is such a successful invader.
Predation on lizard eggs by ants: species interactions in a variable physical environment
Oecologia, 1999
One explanation for long-term¯uctuations in population density is that the intensity of interactions between species is variable. A population can experience variation in the intensity of a species interaction if (1) the density of species with which it directly interacts changes and/or (2) the strength of the interaction (i.e., per capita eects) changes. At Barro Colorado Island, Panama, the tropical lizard Anolis limifrons exhibits wide annual uctuations in density. Previous studies have indicated that (1) the density of A. limifrons is negatively correlated with the amount of wet-season rainfall, (2)¯uctuations in density are related more to variation in egg mortality than to variation in lizard mortality or to fecundity, and (3) most egg mortality is the result of predation by Solenopsis ants. We hypothesized that the amount of wet-season rainfall indirectly alters the density of A. limifrons by producing variation in the intensity of egg predation by Solenopsis. Additionally, we also wanted to determine if variation in the amount of egg mortality was in¯uenced more by variation in the density of Solenopsis, or by variation in the rate of predation. We tested this hypothesis by manipulating litter moisture on experimental plots to simulate the wettest (HW) and driest (LW) wet seasons in the last 20 years, and then monitoring the density of Solenopsis, amount of egg mortality, and rate of predation. The amount of egg mortality was greater on the HW than on the LW treatment and all egg mortality resulted from predation by Solenopsis. ANCOVA indicated that the amount of egg mortality was signi®cantly higher on plots with a greater density of Solenopsis. Treatment eects, however, explained more of the variation in the amount of egg mortality than did Solenopsis density. Our water manipulations did not change the density of Solenopsis, but Solenopsis found and attacked eggs faster on the HW than on the LW treatment. This suggests that moisture during the wet season modi®ed the strength of the interaction between Solenopsis and A. limifrons, supporting the hypothesis that annual variation in the amount of wet-season rainfall indirectly produces parallel variation in annual density of lizard populations by modifying the rate of ant predation on eggs.
Evading invaders: the effectiveness of a behavioral response acquired through lifetime exposure
Behavioral Ecology, 2012
Understanding the mechanisms driving adaptations to survive agonistic interactions, and their function, provides insight into how native species adapt to aggressive invaders, a growing global threat. We staged encounters between native fence lizards (Sceloporus undulatus) and red imported fire ants (Solenopsis invicta) on and off the ant mound (nest) to examine the effectiveness of lizard antipredator behavior through ontogeny while focusing on the impact of lifetime and evolutionary exposure to this invasive threat. We used field-caught and lab-reared lizards from a fire ant-invaded and an uninvaded site. In ;90% of cases, fire ants found lizards within 12 min in natural lizard habitat. Lizards that performed rapid twitches of their body and/or fled after initial encounter with a fire ant scout reduced their risk of having additional fire ants recruit to the attack. The majority of lizards that had been exposed to fire ants within their lifetime (field-caught lizards from the invaded site) behaviorally responded to attack, whereas relatively few lizards that were naïve to fire ants (all lab-reared lizards and field-caught lizards from the uninvaded site) responded. Because fewer adult lizards responded to fire ants than juveniles, they were recruited to by additional attacking ants significantly more than were juveniles. Our data suggest that the higher percentage of responsive adults within invaded populations is the result of within-lifetime selection acting against unresponsive adults, and/or lifetime exposure to fire ants triggering the retention of this juvenile behavior into adulthood, rather than selection acting on a heritable trait across generations.
Animal Behaviour, 2020
The human-assisted movement of species beyond their native range facilitates novel interactions between invaders and native species that can determine whether an introduced species becomes invasive and the nature of any consequences for native communities. Avoiding costly interactions through recognition and avoidance can be compromised by the naïvety of native species to novel invaders and vice versa. We tested this hypothesis using the common wall lizard, Podarcis muralis, and the native lizard species with which it may now interact in Britain (common lizard, Zootoca vivipara, sand lizard, Lacerta agilis) and on Vancouver Island (northern alligator lizard, Elgaria coerulea) by exploring species' responses (tongue flicks, avoidance behaviour) to heterospecific scent cues in controlled experiments. The tongue flick response of P. muralis depended on the different species' scent, with significantly more tongue flicks directed to E. coerulea scent than the other species and the control. This recognition did not result in any other behavioural response in P. muralis (i.e. attraction, aggression, avoidance). Lacerta agilis showed a strong recognition response to P. muralis scent, with more tongue flicks occurring close to the treatment stimuli than the control and aggressive behaviour directed towards the scent source. Conversely, Z. vivipara spent less time near P. muralis scent cues than the control but its tongue flick rate was higher towards this scent in this reduced time, consistent with an avoidance response. There was no evidence of E. coerulea recognition of P. muralis scent in terms of tongue flicks or time spent near the stimuli, although the native species did show a preference for P. muralis-scented refuges. Our results suggest a variable response of native species to the scent of P. muralis, from an avoidance response by Z. vivipara that mirrors patterns of exclusion observed in the field to direct aggression observed in L. agilis and an ambiguous reaction from E. coerulea which may reflect a diminished response to a cue with a low associated cost. These results have significant implications for the invasive success and potential impacts of introduced P. muralis populations on native lizards.