Reproductive trait variation in the functionally dioecious and morphologically heterostylous island endemic Chassalia corallioides (Rubiaceae)

Abstract

Documenting the floral biology and breeding system of species throughout the Rubiaceae family provides data on the number of times heterostyly and dioecy may have evolved in this large family. The objectives of this paper are to quantify (a) whether Chassaliu corallioides, a small tree endemic to L a Rtunion Island in the Indian Ocean, is another example of the evolution of dioecy from distyly and (b) whether reproductive traits linked to male and female function vary over the ecological distribution of this species. Quantification of pollen production and fruit set following controlled and natural pollinations demonstrate that this species is dioecious. Male flowers have longer corolla tubes than female flowers. Female flowers have long styles with stigmas placed above the anthers whereas males have short styles with stigmas placed below the anthers. Stigmas and anthers are reciprocally placed in each morph, illustrating that the species is morphologically heterostylous. Both fecundity and flower size are negatively correlated with altitude. In male plants, corollas are shorter and wider and anthers are placed closer to the mouth of the corolla tube with increasing altitude. Male plants flowered more often than female plants, the likely cause of the male biased sex ratio in each of the two years studied. The evolution of dioecy in relation to the island biogeography of the region and the diversification of the genus Chmsalia is discussed.

Pollen flow in the distylous Palicourea fendleri (Rubiaceae): an experimental test of the Disassortative Pollen Flow Hypothesis

“…In Rubiaceae, this includes at least two dioecious species, Mussaenda parviflora (Naiki and Kato 1999) and Chassalia coralloides (Pailler et al 1998), in which the thrum morph becomes male while the pin morph becomes female. An asymmetry in disassortative pollen flow has been observed in Rubiaceae species, including distylous Palicourea lasiorrachis (Feinsinger and Busby 1987), in which the same patterns of pollen flow of Palicourea fendleri were observed.…”

An angiosperm-wide analysis of the gynodioecy–dioecy pathway

“…Although gender specialization and/or dissortative mating have been reported in a few heterodichogamous species (Pendleton et al, 2000;Gleiser et al 2008), no direct evidence has been found for the heterodichogamy pathway. The evolution to dioecy from distyly has been inferred in some lineages (Pailler et al, 1998, and references therein; Rosas and Dominguez, 2008). However, the rareness of these reproductive systems (distyly, heterodichogamy and androdioecy have been documented in 28, 11 and 12 families, respectively; Renner 2001; Barrett, 2002;Pannell, 2002) suggests that other pathways to dioecy may be more common.…”

Distilia e homostilia em espécies de Palicourea Aubl. (Rubiaceae) do Cerrado do Brasil Central

“…Acredita-se que a distilia tenha surgido mais de uma vez na família, porém para Palicourea esta característica é considerada monofi lética e comum em quase todas as espécies (Pailler & Thompson 1997, Taylor 1997. Embora a distilia seja considerada primitiva e bem estabelecida na família e também no gênero, estudos encontraram diversas modifi cações evolutivas (Bawa & Beach 1983, Sobrevila et al 1983, Hamilton 1990, Richards & Koptur 1993, Pailler et al 1998, Faivre & McDade 2001, Coelho & Barbosa 2003, Castro et al 2004, Consolaro et al 2005. É relatado que a distilia pode originar a dioicia e o monomorfi smo (Ganders 1979, Sobrevila et al 1983, Hamilton 1990, contudo para Palicourea parece que a homostilia é a forma derivada mais comum.…”