BackgroundAt high densities, terrestrial and marine species often employ alternate reproductive tactics (ARTs) to maximize reproductive benefits. We describe ARTs in a high-density and unfished spawning aggregation of the squaretail grouper (Plectropomus areolatus) in Lakshadweep, India.ResultsAs previously reported for this species, territorial males engage in pair-courtship, which is associated with a pair-spawning tactic. Here, we document a previously unreported school-courtship tactic; where territorial males court multiple females in mid-water schools, which appears to culminate in a unique ‘school-spawning’ tactic. Courtship tactics were conditional on body size, local mate density and habitat, likely associated with changing trade-offs between potential mating opportunities and intra-sexual competition. Counter-intuitively, the aggregation showed a habitat-specific inverse size-assortment: large males courted small females on the reef slope while small males courted equal-sized or larger females on the shelf. These patterns remained stable across two years of observation at high, unfished densities.ConclusionsThese unique density-dependent behaviours may disappear from this aggregation as overall densities decline due to increasing commercial fishing pressure, with potentially large consequences for demographics and fitness.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-017-0120-5) contains supplementary material, which is available to authorized users.
Nearly 90% of flowering plants depend on animals for reproduction. One of the main rewards plants offer to pollinators for visitation is nectar. Nesocodon mauritianus (Campanulaceae) produces a blood-red nectar that has been proposed to serve as a visual attractant for pollinator visitation. Here, we show that the nectar’s red color is derived from a previously undescribed alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its characteristic red color. Three enzymes secreted into the nectar are either necessary or sufficient for pigment production, including a carbonic anhydrase that increases nectar pH, an aryl-alcohol oxidase that produces a pigment precursor, and a ferritin-like catalase that protects the pigment from degradation by hydrogen peroxide. Our findings demonstrate how these three enzymatic activities allow for the condensation of sinapaldehyde and proline to form a pigment with a stable imine bond. We subsequently verified that synthetic nesocodin is indeed attractive to Phelsuma geckos, the most likely pollinators of Nesocodon. We also identify nesocodin in the red nectar of the distantly related and hummingbird-visited Jaltomata herrerae and provide molecular evidence for convergent evolution of this trait. This work cumulatively identifies a convergently evolved trait in two vertebrate-pollinated species, suggesting that the red pigment is selectively favored and that only a limited number of compounds are likely to underlie this type of adaptation.
We revise the taxonomy of the agamid genus Sitana Cuvier, 1829, a widely distributed terrestrial lizard from the Indian subcontinent based on detailed comparative analyses of external morphology, osteology and molecular data. We sampled 81 locations spread over 160,000 km2 in Peninsular India including type localities, which represented two known and five previously undescribed species. Based on general similarity in body shape and dewlap all species were hitherto identified as members of the genus Sitana. However, Sitana deccanensis and two other morphotypes, which are endemic to north Karnataka and Maharashtra in Peninsular India, are very distinct from the rest of the known members of the genus Sitana based on their external morphology and osteology. Moreover, members of this distinct morphological group were monophyletic in the molecular tree, and this clade (clade 1) was sister to two well-supported clades (2 and 3) constituting the rest of the Sitana . The interclade genetic divergence in mtDNA between clade 1 and clades 2 and 3 was 21-23%, whereas clade 2 and clade 3 exhibited 14- 16% genetic divergence. Thus, we designate a new genus name “Sarada ” gen. nov. for species represented in Clade 1, which also includes the recently resurrected Sitana deccanensis . We describe two new species in Sarada gen. nov. and three new species in Sitana . Similarity in the dewlap of Sitana and Sarada gen. nov. is attributed to similar function (sexual signaling) and similarity in body shape is attributed to a similar terrestrial life style and/or common ancestry.
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