Adaptive Melanin Response of the Soil Fungus Aspergillus niger to UV Radiation Stress at “Evolution Canyon”, Mount Carmel, Israel

BACKGROUND:Adaptation is an evolutionary process in which traits in a population are tailored by natural selection to better meet the challenges presented by the local environment. The major discussion relating to natural selection concerns the portraying of the cause and effect relationship between a presumably adaptive trait and selection agents generating it. Therefore, it is necessary to identify trait(s) that evolve in direct response to selection, enhancing the organism's fitness. "Evolution Canyon" (EC) in Israel mirrors a microcosmic evolutionary system across life and is ideal to study natural selection and local adaptation under sharply, microclimatically divergent environments. The south-facing, tropical, sunny and xeric "African" slope (AS) receives 200%-800% higher solar radiation than the north-facing, temperate, shady and mesic "European" slope (ES), 200 meters apart. Thus, solar ultraviolet radiation (UVR) is a major selection agent in EC influencing the organism-environment interaction. Melanin is a trait postulated to have evolved for UV-screening in microorganisms. Here we investigate the cause and effect relationship between differential UVR on the opposing slopes of EC and the conidial melanin concentration of the filamentous soil fungus Aspergillus niger. We test the working hypothesis that the AS strains exhibit higher melanin content than strains from the ES resulting in higher UV resistance. METHODOLOGY/PRINCIPAL FINDINGS:We measured conidial melanin concentration of 80 strains from the EC using a spectrophotometer. The results indicated that mean conidial melanin concentration of AS strains were threefold higher than ES strains and the former resisted UVA irradiation better than the latter. Comparisons of melanin in the conidia of A. niger strains from sunny and shady microniches on the predominantly sunny AS and predominantly shady ES indicated that shady conditions on the AS have no influence on the selection on melanin; in contrast, the sunny strains from the ES displayed higher melanin concentrations. CONCLUSIONS/SIGNIFICANCE:We conclude that melanin in A. niger is an adaptive trait against UVR generated by natural selection

Muntingia calabura - an attractive food plant of Cynopterus sphinx -deserves planting to lessen orchard damage

Of the 14 species of pteropodid bats that are found in India, Cynopterus sphinx receives most of the blame for causing damage to commercial fruit crops. We observed the number of visits made by C. sphinx to four species of commercial fruits in orchards (Mangifera indica, Achras sapota, Psidium guajava and Vitis vinifera), and four species of wild/non-commercial fruits (Muntingia calabura, Ficus bengalensis, F. religiosa and Bassia latifolia) in suburban areas. The total number of bat visits to M. calabura was significantly greater than to all other fruit species. The range of percentages of total nightly bat visits was from as low as 5% (V. vinifera) to 47% (F. religiosa), in comparison to the total nightly visits made to M. calabura. In addition, the number of mist-netted individuals of C. sphinx per hour near M. calabura was also significantly higher than near other fruit species. We suggest that if M. calabura is grown in and around orchards, damage caused by C. sphinx to commercial fruit crops may be decreased and therefore would serve as a non-destructive method for managing removal of commercial fruits by bats

In situ feeding tactics of short-nosed fruit bat (Cynopterus sphinx) on mango fruits: evidence of extractive foraging in a flying mammal

We report a sequence of behaviors exhibited by the short-nosed fruit bat Cynopterus sphinx while feeding on fruits of Mangifera indica. They peel off the outer skin to form a feeding area of about 3-6 cm diameter. Such food preparatory behaviors were more pronounced on larger mangoes. Bats competed among themselves to feed on the mangoes that had such feeding areas exposed. Individuals that spent a considerable amount of time on food preparatory behaviors actively secured the fruits. Altogether, these behaviors indicate that Cynopterus bats might have learnt, over evolutionary time, and developed behaviors that facilitate efficient processing and feeding of fruits such as mangoes. It appears that actions exhibited by C. sphinx in peeling off the outer skin of mangoes exemplify "extractive foraging", a behavior that is prominently known in large-brained mammals. Thus, our findings will have implications on the distribution and evolution of extractive foraging and "technical intelligence" among mammalian lineages

Spiny mice modulate eumelanin to pheomelanin ratio to achieve cryptic coloration in "evolution canyon," Israel.

Coat coloration in mammals is an explicit adaptation through natural selection. Camouflaging with the environment is the foremost evolutionary drive in explaining overall coloration. Decades of enquiries on this topic have been limited to repetitive coat color measurements to correlate the morphs with background/habitat blending. This led to an overwhelming endorsement of concealing coloration as a local phenotypic adaptation in animals, primarily rodents to evade predators. However, most such studies overlooked how rodents actually achieve such cryptic coloration. Cryptic coloration could be attained only through optimization between the yellow- to brown-colored "pheomelanin" and gray to black-colored "eumelanin" in the hairs. However, no study has explored this conjecture yet. "Evolution Canyon" (EC) in Israel is a natural microscale laboratory where the relationship between organism and environment can be explored. EC is comprised of an "African" slope (AS), which exhibits a yellow-brownish background habitat, and a "European" slope (ES), exhibiting a dark grayish habitat; both slopes harbor spiny mice (Acomys cahirinus). Here, we examine how hair melanin content of spiny mice living in the opposing slopes of EC evolves toward blending with their respective background habitat.We measured hair-melanin (both eumelanin and pheomelanin) contents of 30 spiny mice from the EC using high-performance liquid chromatography (HPLC) that detects specific degradation products of eumelanin and pheomelanin. The melanin pattern of A. cahirinus approximates the background color of the slope on which they dwell. Pheomelanin is slightly (insignificantly) higher in individuals found on the AS to match the brownish background, whereas individuals of the ES had significantly greater eumelanin content to mimic the dark grayish background. This is further substantiated by a significantly higher eumelanin and pheomelanin ratio on the ES than on the AS.It appears that rodents adaptively modulate eumelanin and pheomelanin contents to achieve cryptic coloration in contrasting habitats even at a microscale

Eumelanin/Pheomelanin ratio of <i>A. cahirinus</i> from “Evolution Canyon” I, Israel.

<p>(A) in the opposite slopes, (B) across stations. Means with the same letter are not significantly different according to Waller-Duncan k-ratio t-test.</p

Contents of eumelanin and pheomelanin in hairs of spiny mice (<i>Acomys cahirinus</i>) from “Evolution Canyon” I, Israel.

<p>(A) in the opposite slopes, (B) across stations. Means with the same letter are not significantly different according to Waller-Duncan k-ratio t-test.</p

Habitat divergence in “Evolution Canyon”.

<p>(A) photo showing part of the “African” slope (AS)/south-facing slope (SFS) of EC, characterized by light terra rossa soil with a stretch of grass cover that generates a yellow-brownish background. (B) Photo of part of the “European” slope (ES)/north-facing slope (NFS), characterized by dark terra rossa soil and shady, humus-laden dark background.</p