Contexts in source publication

Context 1

... was signiÞcantly greater in south-facing ßowers than in north-facing ßowers ( ␹ 2 ϭ 13.29; df ϭ 1; P ϭ 0.0003; Table 1). From the two species of Formicidae collected, only Brachymyrmex heeri Forel was signiÞcantly more abundant in the south-facing ßowers than in the north-facing ones ( ␹ 2 ϭ 78.47; df ϭ 1; P Ͻ 0.0001; Table 1). Likewise, four out of the six species of Coleoptera collected had signiÞcantly different abundance in ßowers with contrasting orientation. Carpophilus lugubris Murray ( ␹ 2 ϭ 10.71; df ϭ 1; P ϭ 0.0011) and Carpophilus hemipterus (L.) ( ␹ 2 ϭ 46.54, df ϭ 1, P Ͻ 0.0001) were signiÞcantly more abundant in south- facing ßowers. Moreover, Chryptophagus sp. ( ␹ 2 ϭ 6; df ϭ 1; P ϭ 0.014) and Urophorus sp. ( ␹ 2 ϭ 4.54; df ϭ 1; P ϭ 0.033) were signiÞcantly more abundant within north-facing ßowers (Table 1); however, these differences in abundances where lost once the sequential Bonferroni correction was applied. In contrast, there were not signiÞcant differences in the abundance of Crematogaster sp., Carpophilus sp. 1, and Carpophilus sp. 2 (Coleoptera) between ßowers with contrasting orientation (1.00 Յ ␹ 2 Յ 3; df ϭ 1; P Ն 0.0896; Table 1). Thysanoptera was the third most abundant group of insects found within the ßowers of P. weberi (152 individuals). Neither the total abundance of thrips ( ␹ 2 ϭ 0.237, df ϭ 1, P ϭ 0.626), nor the abundance of each species of thrips were signiÞcantly different between ßowers with contrasting orientations (0.04 Յ ␹ 2 Յ 2.0; df ϭ 1; P Ն 0.157; Table 1). Relative abundance curves showed that B. heeri was the dominant species in both north- and south- facing ßowers (56 and 62%, respectively; Fig. 2). Insect Diversity. Total diversity (ShannonÐWiener Index) was signiÞcantly greater in ßowers facing toward the north (1.612) than those facing southwards (1.387; t ϭ 2.602, P ϭ 0.009). Similarly, Formicidae and Coleoptera were signiÞcantly more diverse ( t 334 ϭ 3.014, P ϭ 0.003, and t 133 ϭ 4.369, P Ͻ 0.0001, respectively) in north-facing ßowers (0.215 and 1.448, respectively) than in ßowers facing southwards (0.063 and 0.951, respectively). However, the diversity of Thysanoptera was similar between ßowers with orientation north (0.822) and south (1.105; t 149 ϭ Ϫ 1.711, P ϭ 0.271). Similarity. The communities of insects found within ßowers of P. weberi with contrasting orientations were relatively similar, with a 75.86% of similarity (So ̈ rensen index). The communities of Hemiptera and Formicidae were equal between ßowers with different orientation (100% in both cases), whereas the communities of Coleoptera and Thysanoptera were 72.72% similar between orientations. Insect Abundance and Flower Size. Regression analyses showed that the abundance of Coleoptera was well predicted by ßower volume in south-facing ßowers ( F 1, 14 ϭ 20.22; P ϭ 0.0003; r 2 ϭ 0.543; Fig. 3). This result indicates that the abundance of Coleoptera in south-facing ßowers depends upon ßower volume. On the contrary, the abundance of all the other groups of insects was not signiÞcantly associated with ßower volume, in both north- and south-facing ßowers. In this article, we showed that ßower orientation of P. weberi does not affect insect species richness. However, species abundance and diversity was different in ßowers with contrasting orientations. In general, per species-abundance was higher within ßowers facing southwards than in north-facing ßowers. Conversely, species diversity was higher in north-facing ßowers. This last result is surprising and contradicts our hypothesis that diversity was expected to be higher in the most productive oriented ßowers. Although it has been acknowledged that at a regional scale there is a positive relationship between diversity and productivity (see Godfray and Lawton 2001), our result showing that insect communities associated with the less productive ßowers of P. weberi have higher diversity, is consistent with recent reviews in which it ...

Context 2

... that the productivityÐ diversity relationship is likely scale-dependent (Abrams 1995, Waide et al. 1999, Godfray and Lawton 2001). Numerous studies have suggested that there is a positive relationship between PAR and productivity; thus, higher PAR entails higher productivity (Becerra- Rodr ́ guez et al. 1976, Garc ́ a de Corta ́ zar and Nobel 1986, Geller and Nobel 1986). Other studies conducted on the same year and ßowering season, with some of the same individual plants of P. weberi that we used for this study support our hypothesis that the south-facing branches of this cactus species have higher productivity than the north-facing ones. For instance, south-facing branches of P. weberi receive 18.19% more total daily PAR than the north-facing ones on mid-spring (Figueroa-Castro and Valverde 2011); ßowers produced on the south-face of the stems are larger (Co ́ rdova-Acosta 2011), and produce a higher number of ovules per ovary (Figueroa-Castro and Valverde 2011), and pollen grains per ßoral bud (Aguilar-Garc ́ a 2012) than those facing northwards. Likewise, fruits produced on the south face of the branches contain more and heavier seeds than those facing toward the north (Figueroa-Castro and Valverde 2011). Although insect species richness was not signiÞcantly different in ßowers of P. weberi with contrasting orientations, total abundance, and abundance of Formicidae, Coleoptera, and Orius sp. (the only Hemiptera collected) were higher within ßowers facing southwards than in north-facing ßowers. These results point out that south-facing ßowers are more productive habitats capable to maintain high population densities; thus, favoring the most competitive species, which in turn, might exclude other less competitive species (Begon et al. 2006). Likewise, we expected that the communities of insects associated with south-facing ßowers would have higher diversity than those from north-facing ßowers. On the contrary, we found that the less productive north-facing ßowers had the highest total diversity of insects as well as the diversity of Formicidae and Coleoptera. These results are determined by the relative abundance of each species, as species richness did not differ signiÞcantly between ßowers with contrasting orientations. Indeed, the species rank-abun- dance plot ( Fig. 2) showed similar curves for north- and south-facing ßowers. However, this last one had a steeper curve, suggesting a lower equitable species distribution and a stronger dominance by a few, abundant groups. There are at least three possible argu- ments that might explain the low diversity found in the highly productive, south-facing ßowers. First, the steepest speciesÐabundance curve of south-facing ßowers suggests a geometric series distribution (Fig. 2). This pattern is expected when species colonize a novel, unsaturated, or empty habitat (May 1975, Magurran 2004), such as the newly opened ßowers of P. weberi. Such communities are expected to be small, simple, and governed by one or a few dominant factors (May 1975). For instance, in south- facing ßowers, Coleoptera showed the steepest species abundance curve (open squares in Fig. 2) and ßower size (estimated as ßower volume) explained 54% of its abundance (Fig. 3). In contrast, in north- facing ßowers, Coleoptera showed more equitability (open diamonds in Fig. 2) and its abundance was not explained by ßower volume. Accordingly, highly productive ßowers facing southwards are dominated by a few competitive species. Second, it has been suggested that in high productive environments, predators are so abundant that their populations might cause a decrease in the diversity of the community (Godfray and Lawton 2001). In our study, the abundance of B. heeri (Hymenoptera: Formicidae) and Orius sp. (Hemiptera: Anthocoridae) was higher within south-facing ßowers. Formicidae and Anthocoridae are considered predator species on or within ßowers (Inoue et al. 1990, Funderburk et al. 2000, Waipara et al. 2005). B. heeri is omnivore (Delabie et al. 2000), whereas the genus Orius is an active predator (Funderburk et al. 2000, Baez et al. 2004, Atakan and Gencer 2008). Particularly, species within the Orius genus have been found feeding on thrips, aphids, and soft-bodied insects (Frost 1979, Funderburk et al. 2000). Therefore, it is possible that the highest abundance of predator species such as Orius and B. heeri within south-facing ßowers of P. weberi explain, at least partially, the low diversity index recorded on those ßowers. Finally, it has been suggested that environments with high productivity show a decrease in the spatial heterogeneity of resources; thus, experiencing a re- duction in the number of coexisting species (Tilman 1982, Abrams 1995). In our study, the diversity of Coleoptera was signiÞcantly lower in ßowers facing toward the south. Nitidulidae beetles are considered phytophagous of many plants and have been observed feeding on pollen (Inoue et al. 1990, Funderburk et al. 2000); thus, pollen might be the resource that this insect group searches for within the ßowers of P. weberi. According to Aguilar-Garc ́ a (2012), the vari- ance of pollen grain size of P. weberi is marginally lower in ßoral buds oriented toward the south. Thus, south-facing ßowers might represent an environment with lower heterogeneity of resources (i.e., pollen grains) available for the Nitidulidae beetles. Therefore, this might explain the low diversity of Coleoptera within south-facing ßowers. The hypothesis proposing the existence of a positive relationship between productivity and species diversity is well-known (Brown 1988, Mittelbach et al. 2001). However, this hypothesis does not explain the well-documented decrease in species richness in highly productive environments (Brown 1988). Such inconsistency might be caused by differences in spatial scale (Waide et al. 1999). Recent evidence suggests a more complex and scale-dependent relationship between productivity and diversity (Waide et al. 1999, Godfray and Lawton 2001, Magurran 2004). For instance, at a regional scale, diversity increases mono- tonically with productivity; however, at a local scale, the increase is unimodal (Godfray and Lawton 2001). In addition, a meta-analysis performed by Waide et al. (1999) revealed that 12% of the productivityÐ ...

Context 3

... that the productivityÐ diversity relationship is likely scale-dependent (Abrams 1995, Waide et al. 1999, Godfray and Lawton 2001). Numerous studies have suggested that there is a positive relationship between PAR and productivity; thus, higher PAR entails higher productivity (Becerra- Rodr ́ guez et al. 1976, Garc ́ a de Corta ́ zar and Nobel 1986, Geller and Nobel 1986). Other studies conducted on the same year and ßowering season, with some of the same individual plants of P. weberi that we used for this study support our hypothesis that the south-facing branches of this cactus species have higher productivity than the north-facing ones. For instance, south-facing branches of P. weberi receive 18.19% more total daily PAR than the north-facing ones on mid-spring (Figueroa-Castro and Valverde 2011); ßowers produced on the south-face of the stems are larger (Co ́ rdova-Acosta 2011), and produce a higher number of ovules per ovary (Figueroa-Castro and Valverde 2011), and pollen grains per ßoral bud (Aguilar-Garc ́ a 2012) than those facing northwards. Likewise, fruits produced on the south face of the branches contain more and heavier seeds than those facing toward the north (Figueroa-Castro and Valverde 2011). Although insect species richness was not signiÞcantly different in ßowers of P. weberi with contrasting orientations, total abundance, and abundance of Formicidae, Coleoptera, and Orius sp. (the only Hemiptera collected) were higher within ßowers facing southwards than in north-facing ßowers. These results point out that south-facing ßowers are more productive habitats capable to maintain high population densities; thus, favoring the most competitive species, which in turn, might exclude other less competitive species (Begon et al. 2006). Likewise, we expected that the communities of insects associated with south-facing ßowers would have higher diversity than those from north-facing ßowers. On the contrary, we found that the less productive north-facing ßowers had the highest total diversity of insects as well as the diversity of Formicidae and Coleoptera. These results are determined by the relative abundance of each species, as species richness did not differ signiÞcantly between ßowers with contrasting orientations. Indeed, the species rank-abun- dance plot ( Fig. 2) showed similar curves for north- and south-facing ßowers. However, this last one had a steeper curve, suggesting a lower equitable species distribution and a stronger dominance by a few, abundant groups. There are at least three possible argu- ments that might explain the low diversity found in the highly productive, south-facing ßowers. First, the steepest speciesÐabundance curve of south-facing ßowers suggests a geometric series distribution (Fig. 2). This pattern is expected when species colonize a novel, unsaturated, or empty habitat (May 1975, Magurran 2004), such as the newly opened ßowers of P. weberi. Such communities are expected to be small, simple, and governed by one or a few dominant factors (May 1975). For instance, in south- facing ßowers, Coleoptera showed the steepest species abundance curve (open squares in Fig. 2) and ßower size (estimated as ßower volume) explained 54% of its abundance (Fig. 3). In contrast, in north- facing ßowers, Coleoptera showed more equitability (open diamonds in Fig. 2) and its abundance was not explained by ßower volume. Accordingly, highly productive ßowers facing southwards are dominated by a few competitive species. Second, it has been suggested that in high productive environments, predators are so abundant that their populations might cause a decrease in the diversity of the community (Godfray and Lawton 2001). In our study, the abundance of B. heeri (Hymenoptera: Formicidae) and Orius sp. (Hemiptera: Anthocoridae) was higher within south-facing ßowers. Formicidae and Anthocoridae are considered predator species on or within ßowers (Inoue et al. 1990, Funderburk et al. 2000, Waipara et al. 2005). B. heeri is omnivore (Delabie et al. 2000), whereas the genus Orius is an active predator (Funderburk et al. 2000, Baez et al. 2004, Atakan and Gencer 2008). Particularly, species within the Orius genus have been found feeding on thrips, aphids, and soft-bodied insects (Frost 1979, Funderburk et al. 2000). Therefore, it is possible that the highest abundance of predator species such as Orius and B. heeri within south-facing ßowers of P. weberi explain, at least partially, the low diversity index recorded on those ßowers. Finally, it has been suggested that environments with high productivity show a decrease in the spatial heterogeneity of resources; thus, experiencing a re- duction in the number of coexisting species (Tilman 1982, Abrams 1995). In our study, the diversity of Coleoptera was signiÞcantly lower in ßowers facing toward the south. Nitidulidae beetles are considered phytophagous of many plants and have been observed feeding on pollen (Inoue et al. 1990, Funderburk et al. 2000); thus, pollen might be the resource that this insect group searches for within the ßowers of P. weberi. According to Aguilar-Garc ́ a (2012), the vari- ance of pollen grain size of P. weberi is marginally lower in ßoral buds oriented toward the south. Thus, south-facing ßowers might represent an environment with lower heterogeneity of resources (i.e., pollen grains) available for the Nitidulidae beetles. Therefore, this might explain the low diversity of Coleoptera within south-facing ßowers. The hypothesis proposing the existence of a positive relationship between productivity and species diversity is well-known (Brown 1988, Mittelbach et al. 2001). However, this hypothesis does not explain the well-documented decrease in species richness in highly productive environments (Brown 1988). Such inconsistency might be caused by differences in spatial scale (Waide et al. 1999). Recent evidence suggests a more complex and scale-dependent relationship between productivity and diversity (Waide et al. 1999, Godfray and Lawton 2001, Magurran 2004). For instance, at a regional scale, diversity increases mono- tonically with productivity; however, at a local scale, the increase is unimodal (Godfray and Lawton 2001). In addition, a meta-analysis performed by Waide et al. (1999) revealed that 12% of the productivityÐ ...

Context 4

... that the productivityÐ diversity relationship is likely scale-dependent (Abrams 1995, Waide et al. 1999, Godfray and Lawton 2001). Numerous studies have suggested that there is a positive relationship between PAR and productivity; thus, higher PAR entails higher productivity (Becerra- Rodr ́ guez et al. 1976, Garc ́ a de Corta ́ zar and Nobel 1986, Geller and Nobel 1986). Other studies conducted on the same year and ßowering season, with some of the same individual plants of P. weberi that we used for this study support our hypothesis that the south-facing branches of this cactus species have higher productivity than the north-facing ones. For instance, south-facing branches of P. weberi receive 18.19% more total daily PAR than the north-facing ones on mid-spring (Figueroa-Castro and Valverde 2011); ßowers produced on the south-face of the stems are larger (Co ́ rdova-Acosta 2011), and produce a higher number of ovules per ovary (Figueroa-Castro and Valverde 2011), and pollen grains per ßoral bud (Aguilar-Garc ́ a 2012) than those facing northwards. Likewise, fruits produced on the south face of the branches contain more and heavier seeds than those facing toward the north (Figueroa-Castro and Valverde 2011). Although insect species richness was not signiÞcantly different in ßowers of P. weberi with contrasting orientations, total abundance, and abundance of Formicidae, Coleoptera, and Orius sp. (the only Hemiptera collected) were higher within ßowers facing southwards than in north-facing ßowers. These results point out that south-facing ßowers are more productive habitats capable to maintain high population densities; thus, favoring the most competitive species, which in turn, might exclude other less competitive species (Begon et al. 2006). Likewise, we expected that the communities of insects associated with south-facing ßowers would have higher diversity than those from north-facing ßowers. On the contrary, we found that the less productive north-facing ßowers had the highest total diversity of insects as well as the diversity of Formicidae and Coleoptera. These results are determined by the relative abundance of each species, as species richness did not differ signiÞcantly between ßowers with contrasting orientations. Indeed, the species rank-abun- dance plot ( Fig. 2) showed similar curves for north- and south-facing ßowers. However, this last one had a steeper curve, suggesting a lower equitable species distribution and a stronger dominance by a few, abundant groups. There are at least three possible argu- ments that might explain the low diversity found in the highly productive, south-facing ßowers. First, the steepest speciesÐabundance curve of south-facing ßowers suggests a geometric series distribution (Fig. 2). This pattern is expected when species colonize a novel, unsaturated, or empty habitat (May 1975, Magurran 2004), such as the newly opened ßowers of P. weberi. Such communities are expected to be small, simple, and governed by one or a few dominant factors (May 1975). For instance, in south- facing ßowers, Coleoptera showed the steepest species abundance curve (open squares in Fig. 2) and ßower size (estimated as ßower volume) explained 54% of its abundance (Fig. 3). In contrast, in north- facing ßowers, Coleoptera showed more equitability (open diamonds in Fig. 2) and its abundance was not explained by ßower volume. Accordingly, highly productive ßowers facing southwards are dominated by a few competitive species. Second, it has been suggested that in high productive environments, predators are so abundant that their populations might cause a decrease in the diversity of the community (Godfray and Lawton 2001). In our study, the abundance of B. heeri (Hymenoptera: Formicidae) and Orius sp. (Hemiptera: Anthocoridae) was higher within south-facing ßowers. Formicidae and Anthocoridae are considered predator species on or within ßowers (Inoue et al. 1990, Funderburk et al. 2000, Waipara et al. 2005). B. heeri is omnivore (Delabie et al. 2000), whereas the genus Orius is an active predator (Funderburk et al. 2000, Baez et al. 2004, Atakan and Gencer 2008). Particularly, species within the Orius genus have been found feeding on thrips, aphids, and soft-bodied insects (Frost 1979, Funderburk et al. 2000). Therefore, it is possible that the highest abundance of predator species such as Orius and B. heeri within south-facing ßowers of P. weberi explain, at least partially, the low diversity index recorded on those ßowers. Finally, it has been suggested that environments with high productivity show a decrease in the spatial heterogeneity of resources; thus, experiencing a re- duction in the number of coexisting species (Tilman 1982, Abrams 1995). In our study, the diversity of Coleoptera was signiÞcantly lower in ßowers facing toward the south. Nitidulidae beetles are considered phytophagous of many plants and have been observed feeding on pollen (Inoue et al. 1990, Funderburk et al. 2000); thus, pollen might be the resource that this insect group searches for within the ßowers of P. weberi. According to Aguilar-Garc ́ a (2012), the vari- ance of pollen grain size of P. weberi is marginally lower in ßoral buds oriented toward the south. Thus, south-facing ßowers might represent an environment with lower heterogeneity of resources (i.e., pollen grains) available for the Nitidulidae beetles. Therefore, this might explain the low diversity of Coleoptera within south-facing ßowers. The hypothesis proposing the existence of a positive relationship between productivity and species diversity is well-known (Brown 1988, Mittelbach et al. 2001). However, this hypothesis does not explain the well-documented decrease in species richness in highly productive environments (Brown 1988). Such inconsistency might be caused by differences in spatial scale (Waide et al. 1999). Recent evidence suggests a more complex and scale-dependent relationship between productivity and diversity (Waide et al. 1999, Godfray and Lawton 2001, Magurran 2004). For instance, at a regional scale, diversity increases mono- tonically with productivity; however, at a local scale, the increase is unimodal (Godfray and Lawton 2001). In addition, a meta-analysis performed by Waide et al. (1999) revealed that 12% of the productivityÐ ...

Context 5

... that the productivityÐ diversity relationship is likely scale-dependent (Abrams 1995, Waide et al. 1999, Godfray and Lawton 2001). Numerous studies have suggested that there is a positive relationship between PAR and productivity; thus, higher PAR entails higher productivity (Becerra- Rodr ́ guez et al. 1976, Garc ́ a de Corta ́ zar and Nobel 1986, Geller and Nobel 1986). Other studies conducted on the same year and ßowering season, with some of the same individual plants of P. weberi that we used for this study support our hypothesis that the south-facing branches of this cactus species have higher productivity than the north-facing ones. For instance, south-facing branches of P. weberi receive 18.19% more total daily PAR than the north-facing ones on mid-spring (Figueroa-Castro and Valverde 2011); ßowers produced on the south-face of the stems are larger (Co ́ rdova-Acosta 2011), and produce a higher number of ovules per ovary (Figueroa-Castro and Valverde 2011), and pollen grains per ßoral bud (Aguilar-Garc ́ a 2012) than those facing northwards. Likewise, fruits produced on the south face of the branches contain more and heavier seeds than those facing toward the north (Figueroa-Castro and Valverde 2011). Although insect species richness was not signiÞcantly different in ßowers of P. weberi with contrasting orientations, total abundance, and abundance of Formicidae, Coleoptera, and Orius sp. (the only Hemiptera collected) were higher within ßowers facing southwards than in north-facing ßowers. These results point out that south-facing ßowers are more productive habitats capable to maintain high population densities; thus, favoring the most competitive species, which in turn, might exclude other less competitive species (Begon et al. 2006). Likewise, we expected that the communities of insects associated with south-facing ßowers would have higher diversity than those from north-facing ßowers. On the contrary, we found that the less productive north-facing ßowers had the highest total diversity of insects as well as the diversity of Formicidae and Coleoptera. These results are determined by the relative abundance of each species, as species richness did not differ signiÞcantly between ßowers with contrasting orientations. Indeed, the species rank-abun- dance plot ( Fig. 2) showed similar curves for north- and south-facing ßowers. However, this last one had a steeper curve, suggesting a lower equitable species distribution and a stronger dominance by a few, abundant groups. There are at least three possible argu- ments that might explain the low diversity found in the highly productive, south-facing ßowers. First, the steepest speciesÐabundance curve of south-facing ßowers suggests a geometric series distribution (Fig. 2). This pattern is expected when species colonize a novel, unsaturated, or empty habitat (May 1975, Magurran 2004), such as the newly opened ßowers of P. weberi. Such communities are expected to be small, simple, and governed by one or a few dominant factors (May 1975). For instance, in south- facing ßowers, Coleoptera showed the steepest species abundance curve (open squares in Fig. 2) and ßower size (estimated as ßower volume) explained 54% of its abundance (Fig. 3). In contrast, in north- facing ßowers, Coleoptera showed more equitability (open diamonds in Fig. 2) and its abundance was not explained by ßower volume. Accordingly, highly productive ßowers facing southwards are dominated by a few competitive species. Second, it has been suggested that in high productive environments, predators are so abundant that their populations might cause a decrease in the diversity of the community (Godfray and Lawton 2001). In our study, the abundance of B. heeri (Hymenoptera: Formicidae) and Orius sp. (Hemiptera: Anthocoridae) was higher within south-facing ßowers. Formicidae and Anthocoridae are considered predator species on or within ßowers (Inoue et al. 1990, Funderburk et al. 2000, Waipara et al. 2005). B. heeri is omnivore (Delabie et al. 2000), whereas the genus Orius is an active predator (Funderburk et al. 2000, Baez et al. 2004, Atakan and Gencer 2008). Particularly, species within the Orius genus have been found feeding on thrips, aphids, and soft-bodied insects (Frost 1979, Funderburk et al. 2000). Therefore, it is possible that the highest abundance of predator species such as Orius and B. heeri within south-facing ßowers of P. weberi explain, at least partially, the low diversity index recorded on those ßowers. Finally, it has been suggested that environments with high productivity show a decrease in the spatial heterogeneity of resources; thus, experiencing a re- duction in the number of coexisting species (Tilman 1982, Abrams 1995). In our study, the diversity of Coleoptera was signiÞcantly lower in ßowers facing toward the south. Nitidulidae beetles are considered phytophagous of many plants and have been observed feeding on pollen (Inoue et al. 1990, Funderburk et al. 2000); thus, pollen might be the resource that this insect group searches for within the ßowers of P. weberi. According to Aguilar-Garc ́ a (2012), the vari- ance of pollen grain size of P. weberi is marginally lower in ßoral buds oriented toward the south. Thus, south-facing ßowers might represent an environment with lower heterogeneity of resources (i.e., pollen grains) available for the Nitidulidae beetles. Therefore, this might explain the low diversity of Coleoptera within south-facing ßowers. The hypothesis proposing the existence of a positive relationship between productivity and species diversity is well-known (Brown 1988, Mittelbach et al. 2001). However, this hypothesis does not explain the well-documented decrease in species richness in highly productive environments (Brown 1988). Such inconsistency might be caused by differences in spatial scale (Waide et al. 1999). Recent evidence suggests a more complex and scale-dependent relationship between productivity and diversity (Waide et al. 1999, Godfray and Lawton 2001, Magurran 2004). For instance, at a regional scale, diversity increases mono- tonically with productivity; however, at a local scale, the increase is unimodal (Godfray and Lawton 2001). In addition, a meta-analysis performed by Waide et al. (1999) revealed that 12% of the productivityÐ ...