Friday, November 6, 2015

[Botany • 2015] Besleria macropoda (Gesneriaceae): Lectotypification, Distribution, Functional Epiphylly and Discordant Fruit Morphology of A Rare Costa Rican Endemic


FIGURE 2. Besleria macropoda, epiphyllous position of flowers and fruits.
A. Shoot. B. Inflorescence with open flowers. C. Infructescence showing fruits with split and reflexed carpel walls exposing red placentae and seeds. D. Sulcate petiole and leaf base clasping the peduncle above the sunken midrib.
(Photos by A. Berger; voucher: Berger & Etl 1443.).DOI: 10.11646/phytotaxa.233.2.2

Abstract

Besleria macropoda, a rare and poorly known gesneriad endemic to Costa Rica, was recently collected for the first time on the southern slopes of the Fila Costeña (Puntarenas Province, SE Costa Rica). The collection considerably widens the geographic distribution to the southeastern part of Costa Rica. Moreover, the following unique characters not previously addressed in the literature were observed and are documented here: (1) The elongate peduncles of the inflorescences are clamped in a channel formed by the sunken midrib of the leaf, rendering the flowers and fruits positioned in the center of the leaf blade. The epiphyllous appearance of the inflorescence on the leaf surface enhances contrasting colors that may aid the pollination and/or fruit dispersal. (2) The fruits split open irregularly, with the fleshy carpel lobes becoming reflexed. This fruit dehiscence deviates from the indehiscent berries that typically characterize Besleria. This results in displaying a globose head of red placental tissue covered by tiny, red seeds. A preliminary survey of Besleria fruits suggests that this peculiar fruit type is present in at least 15 species representing almost 8% of the genus. Fruit morphology of Besleria is therefore less uniform than previously recognized and the “indehiscent berry” can no longer serve as a distinctive generic character of Besleria, which necessitates consideration in floras and identification keys. In addition, a list of herbarium specimens, lectotypification, a distribution map, IUCN red list assessment and an amended key to diagnose Besleria relative to Gasteranthus are provided.

Keywords: Besleria, Gesneriaceae, fruit morphology, epiphylly, Eudicots, Costa Rica


Conclusions
The recent collection of Besleria macropoda widens the known distribution considerably and highlights two unique characters not previously addressed. The inflorescences/infructescences are functionally epiphyllous possibly aiding in pollination and/or fruit dispersal. Fruit dehiscence deviates from indehiscent berries that typically characterize Besleria: the fruits appear ruptured and split open irregularly, with the fleshy carpel lobes becoming reflexed. This results in displaying a globose head of red placental tissue embedded with tiny, red seeds. In addition to B. macropoda, this specific fruit type was found in 14 other species of the genus. Fruit morphology of Besleria is thus less uniform than previously understood, and the “indehiscent berry” can no longer serve as a distinctive generic character of Besleria, which necessitates consideration in generic keys such as in regional floras. However, further fieldwork is necessary to fully understand the distribution, phylogenetic context, and functional implications of this particular fruit type and fruit dehiscence.


Andreas Berger, John J. Clark and Anton Weber. 2015. Besleria macropoda (Gesneriaceae): Lectotypification, Distribution, Functional Epiphylly and Discordant Fruit Morphology of  A Rare Costa Rican Endemic. Phytotaxa. 233(2): 139–152. DOI: 10.11646/phytotaxa.233.2.2

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