Sex is determined by XY chromosomes across the radiation of dioecious Nepenthes pitcher plants.

Species with separate sexes (dioecy) are a minority among flowering plants, but dioecy has evolved multiple times independently in their history. The sex-determination system and sex-linked genomic regions are currently identified in a limited number of dioecious plants only. Here, we study the sex-determination system in a genus of dioecious plants that lack heteromorphic sex chromosomes and are not amenable to controlled breeding: Nepenthes pitcher plants. We genotyped wild populations of flowering males and females of three Nepenthes taxa using ddRAD-seq and sequenced a male inflorescence transcriptome. We developed a statistical tool (privacy rarefaction) to distinguish true sex specificity from stochastic noise in read coverage of sequencing data from wild populations and identified male-specific loci and XY-patterned single nucleotide polymorphsims (SNPs) in all three Nepenthes taxa, suggesting the presence of homomorphic XY sex chromosomes. The male-specific region of the Y chromosome showed little conservation among the three taxa, except for the essential pollen development gene DYT1 that was confirmed as male specific by PCR in additional Nepenthes taxa. Hence, dioecy and part of the male-specific region of the Nepenthes Y-chromosomes likely have a single evolutionary origin

The Universiti Brunei Darussalam biological collections: history, present assets, and future development

Polgar, T.U, Grafe, H.Y., Pang, Brahim, Cicuzza, J.W., Slik (2018): The Universiti Brunei Darussalam biological collections: history, present assets, and future development. Raffles Bulletin of Zoology 66: 320-336, DOI: http://doi.org/10.5281/zenodo.535874

How a pitcher plant facilitates roosting of mutualistic woolly bats

Question: How does the pitcher plant Nepenthes hemsleyana facilitate roosting of mutualistic bats? Hypothesis: Pitchers have adaptations that match the shape and body size of small woolly bats. Organisms: The pitcher plant Nepenthes hemsleyana, its close relative N. rafflesiana, and the woolly bat Kerivoula hardwickii. Field sites: Peat swamps and heath forests in western Brunei Darussalam on the island of Borneo. Methods: We measured various morphological traits of N. hemsleyana that might facilitate bat roosting and compared them to pitchers of N. rafflesiana that is not visited by bats. We compared the size and characteristics of the pitchers with body sizes of roosting bats. Conclusions: As predicted, aerial pitchers matched the body size of bats and had lower digestive fluid levels than pitchers of a close relative. Thus, small morphological differences between closely related species have caused rapid dietary niche divergence

Different Messages are Transmitted by Individual Duet Contributions and Complete Duets in a Species with Highly Overlapped Duets

Background: Duet function hypotheses have been mostly studied in bird species that produce duets with male and female solo songs. However, in order to understand if patterns of duet function are similar across all duetting species, it is highly necessary to test the duet function hypotheses in species that produce duets with vocalizations other than solo songs. Objective: We studied the responses of territorial pairs to each sex’s individual duet contribution and complete duets in a species that produces duets with a vocalization other than male and female solo songs. Methods: We conducted a playback experiment where we presented duet contributions of each sex to three populations of White-eared Ground-sparrows (Melozone leucotis) in Costa Rica, during this species’ breeding season in 2016. Results: The responses to complete duets were stronger than those to each sex’s duet contribution, suggesting that complete duets and each sex’s duet contribution have different functions. Complete duets are used to protect resources from intruders (supporting the resource defense hypothesis), and to prevent the partner from being usurped by intruders (supporting the mate-guarding hypothesis). Males used solo songs in response to female duet contributions, and this may work to attract intruder females (increasing the probability of extra-pair copulation). Males also use solo songs in response to male duet contributions, which may work as a signal to repel intruder males and guard their female. In this case, where mate attraction occurs with a completely different type of vocalization than used for duetting, we found a clear pattern of a double agenda for males when a territorial intrusion occurs. Conclusions: This study provides strong support for the dual function hypothesis in duets and reveals conflicting selective pressures between pair members relative to each hypothesis.Universidad de Costa Rica/[111-B5-241]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí