Dror Hawlena

Dror Hawlena

Education

PhD, Ben Gurion University of the Negev.

MSc summa cum laude, Ben Gurion University of the Negev.

BSc, Ben Gurion University of the Negev.

Publication

Adout A., Hawlena D, Maman R, Paz-Tal O, Karpas Z, 2007. Determination of trace elements in pigeon and crow feathers by ICPMS. International Journal of Mass Spectrometry 267: 109-116. pdf

Cooper WE, Perez-Mellado V, Hawlena D, 2007. Predator number, speed, and approach path affect escape direction and flight initiation distance. Journal of Herpetology 41:197-204. pdf

Cooper WE, Perez-Mellado V, Hawlena D, 2006. Magnitude of food reward affects escape behavior and acceptable risk in Balearic lizards, Podarcis lilfordi. Behavioral Ecology 17:554-559. pdf

Hawlena D, Boochnik R, Abramsky Z, Bouskila A, 2006. Blue tail and striped body: why do lizards change their infant costume when growing up? Behavioral Ecology 17 889-896. (Featured by: Fox news http://www.foxnews.com/story/0,2933,218060,00.html; LiveSceince: http://www.livescience.com/animals/061005_lizard_tails.html). pdf

Hawlena D, Bouskila A, 2006. Land management practices for combating desertification cause species replacement of desert lizards. Journal of Applied Ecology 43:701-709.(cover picture).pdf

Lopez P, Hawlena D, Polo V, Amo L, Martin J, 2005. Shy-bold inter-individual variations in antipredatory behaviour of male Iberian rock-lizards. Animal Behavior 69:1-9. pdf

Research Interests

My research aims to understand how individual risk management mechanisms are affecting ecological and evolutionary processes. To reduce the probability of being killed, prey should perceive the risk correctly and to respond in ways that minimize its overall fitness loss. Such costly defensive strategies may change interaction strength, inducing indirect consequences on community dynamics and hence on evolutionary processes. This mechanistic approach enables me to develop theory by integrating knowledge from different ecological disciplines and to empirically test it at the individual, population and community levels simultaneously. My multifaceted research program combines field and laboratory experiments in different model systems (reptilian and insect) while integrating concepts and methods from biomechanics, physiology, behavior, ecology and evolution. I am always trying to integrate applied aspects into the conceptual framework of my studies to contribute toward conserving biodiversity

Trapelus savignii in Holot Agur Nature Reserve, Negev Desert, Israel

Past and Current Research

Individual level: I study what repertoire of anti-predator mechanisms do animals use, what factors influencing their risk management decisions and what are the consequences of using those anti-predator mechanisms on their morphology, performances and behavior. Using four different study systems, I showed that prey physiological condition, amount of food reward and evolutionary history play an important role in the ability of individuals to manage predation risk and so do the predator identity, foraging mode and number. I found that lizards that were experimentally exposed to increased avian predation risk were shorter and produced shorter hatchlings with lower body condition and faster sprint speed. My findings indicate that exposure to predation risk may play a dominant role in determining hatchling phenotype and may promote rapid evolution. On the other hand, prey responses to reduce the risk of predation may moderate survival selection and hence can impede evolutionary processes. The possibility that spatial variation in predation risk may affect evolutionary processes has a well established theoretical basis, but has been rarely examined experimentally. My current research aims to test these hypotheses, using grasshoppers (prey) and spiders (predator). This system allows isolating the intimidation component of predation from the consumptive component and enables testing how intimidation affect prey morphology, escape performances, feeding ecology and anti-predator behaviors in consequent generations and to examine the fitness consequences under increased predation and controlled environments.

Balearic lizards (Podarcis lilfordi) assessing food reward (fly maggot number)

During my studies, I became fascinated with prey risk management mechanisms that, at first, appear maladaptive. I adopted approach that examine the role of individual trait as part of a bigger complex of anti-predator mechanisms and suggested that those mechanisms may have adaptive complementary functions. This approach allowed me to explain why do animals use conspicuous display when no conspecifics are present, why do young animals have conspicuous coloration that, apparently, make them more vulnerable to predation and why do they change these characters when growing-up. Another research direction that can explain behaviors that appears non- adaptive in an isolated context is the study of individual syndromes. I studied this phenomenon (collaborating with colleagues from the Museo Nacional de Ciencias Naturales (CSIC), Spain) in laboratory and field conditions and found, for the first time in reptiles, that individuals are using suites of correlated behaviors across situations. Such comprehension can explain the maintenance of individual variation between behavioral types, improving our understanding of ecological and evolutionary processes.

Acanthodactylus beerhsebensis adult (left) and hatchling in the Loess Park, Negev Desert, Israel

Population level: I study the effect of spatial variation in predation on population dynamics. I manipulated the spatial heterogeneity of predation by adding artificial trees that attract predators to habitat patches they could not use before. The supplementation of perches increased the presence of avian predators and generated a source-sink patch dynamic. Lizards (i.e., prey) failed to assess the altered habitat quality accurately, turning the low quality patches to an ecological trap (i.e., sink habitats to which organisms are attracted as though they were of high quality). Inability to assess predation can severely affect the demography of populations in source habitats and may impede character divergence due to rapid gene exchange. Currently, I study whether differences in survivorship or differences in mate preferences between locals and immigrants can limit gene flow between sympatric patches and to allow character divergence.

Community level: I study the effect of predation on community structure through indirect effects on parasitism. I conducted a manipulative field experiments to examine this interaction using shrike (predator) lizard (prey) and parasitic mites. Contrary to previous hypotheses that predicted constant decline in parasitism under elevated predation, I found that parasite abundance can either increased or decrease. I constructed a conceptual model that is based on the assumption that the removal of prey and the risk effect exert different and sometimes contradictory effects on parasite abundance. Currently, I am looking for a model system that will allow me to test my hypotheses.

Acanthodactylus beershebensis that was impaled by southern grey shrike (Lanius meridionalis)

Future Research

I plan to continue developing my research into the multidimensional effect of predation on ecologically based evolutionary processes. I will explore prey risk management mechanisms and their consequences, especially those that could make offspring more adapted to the conditions experienced by the mother. To complement this direction, I will further develop the theory that considered anti-predator mechanisms as a cohesive complex and will empirically test the consequences on the individual fitness and population dynamics. Better understanding of those mechanisms and their consequences will allow me to examine the role of spatial variation in predation on evolutionary process and especially rapid evolution. I want to explore this ultimate goal using a field system that will allow me to integrate all components of my research program in order to look at long-term consequences of spatial variation in predation on community dynamics and evolutionary processes using ecological and molecular tools.