Based on Figures 9, 10, and 11, which is the most significant influence on Lepid

Question

Based on Figures 9, 10, and 11, which is the most significant influence on Lepidodactylus lugubris?

A. interspecific competition

B. intraspecific competition

C.both types of competition are equally important

0.6 LI low LI high IL, low" Lhigh 0.80 Alone +HI LI low LI high |LI low LI high 0.55 0.50 CD 0.45 0.40 0.35 + HI LI low LI high LI low LI high L. lugubris H. frenatus FiG. 9. Foraging success, diet, and strike distance of L lugubris (LA) and H. frenaus (H. Foraging success (A) is the proportion ( SE) of successful captures per attempt for all individuals of a given species within an enclosure during experiment 1, Hemidactylus frenarus had a large negative impact on the foraging success of L. lugubris. Both species preferentially foraged on termite alates, which accounted for 63% of all successful captures in both species. For L* fugabri the proportion 1 SE) of successful captures that were ter- nificantly. However the proportion of termites in L ugubris diet occurred in response to increased intraspecific density Strike distance (C), measured as the proportion of foraging attempts :20 cm ( SE), was not altered significantly for LIM8 ubris in the presence of H. frenatus, however H. frenatus had a greater proportion of longer strikes than L. lugubris. An increase in L ugubris density had little effect on H frenatus foraging (right-hand side. The magnitude of inter- specific competition on lugubris shown by lines) can be compared directly to intraspecific competition (left and center columns)

Explanation / Answer

This effect of habitat structure depends on competitors possessing different foraging strategies. The interaction of topographic structure with the social system of Ll is more complex. Ll attempt to maintain interindividual distances and interact frequently while foraging. Conversely, Hf females show almost no intraspecific aggression, and even though Hf male±male interactions can be intense, they are usually rapid and infrequent (ref. 25; K.P., unpublished data). As predicted, increasing topographic structure did not affect spacing in Hf but had strong effects on Ll social interactions. Interindividual distances were significantly reduced, allowing foraging Ll greater access to regions with higher productivity (Fig. 4A). However, this resulted in an unanticipated increase in agonistic encounters among Ll, and these encounters lasted longer (Fig. 5B). This apparent tradeoff was only directly measured in terms of foraging attempts but may be a factor in the reduced body condition of Ll undergoing intraspecific competition as compared with interspecific competition in structurally complex environments. When resources are clumped, other species with different social systems may respond differently to increased topographic structure. We predict that visually territorial species similar to Ll, with frequent protracted encounters, may be similarly affected by topographic structure. Thecurrentstudyhasdemonstratedthatmanyprocessescan interact with habitat structure in complex ways to affect competition. Three processes known to be affected by habitat structure are commonly observed in most animals. First, predation or the threat of predation is affected by habitat structure, and species respond to this threat (31±33). Second, foraging efficiency for mobile or stationary prey is affected by habitat structure (2, 8±14). Third, social monitoring such as territoriality, interindividual spacing, or reproduction can also be influenced by habitat structure (14±18). Species respond to habitat structure by evolving adaptations, altering behavior, or changing their distribution or abundance. However for many species, the processes of foraging, predation avoidance, and social interaction are likely to be operating simultaneously. Consequently, changes in habitat structure are likely to lead to complex alterations in the interactions between animals. The likelihood of encountering complex responses to changes in habitat structure emphasizes the importance of using a mechanistic approach (19) in future work. Here, we coupled experimental manipulation with quantified behavioral observation to untangle the mechanisms that produce higher order interactions (20). In the long term, empirical mechanistic studies will facilitate development of a theoretical framework; however, in the short term, these studies will help to evaluate similar processes in other systems. Based on the current study, changes in habitat structure that affect competition in other systems may be more accurately predicted by considering basic species attributes such as body size, foraging strategy, and social behavior. Human-induced modifications in Pacific habitats (lights and flat walls) facilitate the invasion of Hf. Other human activities may alter microhabitat structure at different scales. For instance, habitat structure is diminished when mature forests are replaced by monotypic orchards, when underwater vegetation disappears, or when coral reefs die. Resource clumps are created by garbage dumps and heated effluent from power plants. An agricultural field may appear structured, clumped, or neither from the perspective of an herbivore, an insectivore, asmallrodent,alargemammal,oraraptor.Humanalterations of physical habitat structure may directly affect species diversity at higher trophic levels and may not be confined to processes cascading vertically from lower trophic levels

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