Breakdown of distyly and pin‐monomorphism in Psychotria carthagenensis Jacq. (Rubiaceae)

Abstract

Rubiaceae contains the largest number of distylous species in the Angiosperms, but the evolution and control of distyly is poorly understood in this group. Atypical distylous populations and species have been described in this family and associated with disturbance, pollination failure and impaired reproductive success. Some of these atypical taxa belong to Psychotria, the largest genus in the family. In the present study, we investigate the pollination and breeding biology of Psychotria carthagenensis Jacq., a widely distributed species that has been described as typically distylous. Fieldwork was carried out mainly at the Panga Ecological Station, in Uberlândia, MG, Brazil. We carried out phenological observations, floral biology studies and hand pollination experiments within the Panga Ecological Station population. We complemented these data with herbarium and field surveys from elsewhere in Brazil. The studied population bloomed at the beginning of the rains (September-December). The main pollinators were Bombus and small Halictidae bees. The Panga Ecological Station population presented pinmonomorphism with only two thrum individuals in more than 100 flowering individuals surveyed. Hand pollinations at the Panga Ecological Station showed self-compatibility and intramorph compatibility. Typical distyly and isoplethy were found in other areas and both morphs appeared in herbarium material. However, pin-monomorphism was also observed elsewhere in Brazil. Typical distyly, pin-monomorphism and homostyly observed concurrently in Brazilian populations of P. carthagenensis indicate that alternative reproductive strategies, probably favoring selfing, appear to have developed independently in this species.

Atypical distyly in Psychotria goyazensis Mull. Arg. (Rubiaceae), an intramorph self-compatible species

“…Because the number of studies on the reproductive biology of Psychotria species is increasing, it is oft en possible to fi nd the occurrence of monomorphic populations, especially pin species (Ganders 1979, Sakai & Wright 2008Consolaro et al 2011). Th e same pin monomorphism found in P. goyazensis has been also reported in P. carthagenensis (Con- solaro et al 2011) and P. gracilifl ora, P. hoff mannseggiana, P. micrantha and P. tenuifolia (Sakai Wright & 2008).…”

“…The blooming pattern of Rubiaceae and Psychotria species in the cerrado often seems to be linked to the rainy season in this ecosystem (Martin-Gajardo & Morellato 2003, Lopez & Buzato 2005, Consolaro et al 2011. However, the bloom period and the fructification of many species can result not only from abiotic selective pressures, such as the climate system, but also as a way to enhance survival strategies when the species will be able to disperse and germinate its seeds (Sarmiento & Monasterio 1983).…”

“…Th e release of pollen was determined by observation of loose pollen on the anthers. Stigma receptivity was determined by the separation of the stigma lobes (n = 16), which is usually suitable for studies of Rubiaceae (Coelho & Barbosa 2003, Consolaro et al 2005, Consolaro et al 2009, Consolaro et al 2011.…”

“…However, some authors argue that, in certain families (especially Rubiaceae), the morphological and physiological integrity of the supergene diff ers from that seen in other families (Richards 1986;Lewis & Jones 1992;Barrett & Shore 2008;Consolaro et al 2011). Some Rubiaceae genera, such as Psychotria, Palicourea, Coccocypselum, Declieuxia, Sabicea, Guettarda and Manettia, are known to be typically distylous but present anomalies or breakdown of distyly (Sobrevila et al 1983;Hamilton 1990;Richards & Koptur 1993;Passos & Sazima 1995;Faivre & McDade 2001, Coelho & Barbosa 2003Consolaro et al 2009).…”

“…In recent decades, the number of studies on heterostyly and phenology of heterostylous species in the cerrado has been increasing (Monteiro et al 1991;Coelho & Barbosa 2003;Coelho & Barbosa 2004;Consolaro et al 2005;Toledo et al 2007;Lenza et al 2008;Oliveira 2008;Consolaro et al 2009;Machado et al 2010;Consolaro et al 2011) and could be compared to those conducted in the Atlantic Forest (Passos & Sazima 1995;Lopes & Buzato 2005;Castro & Oliveira 2002;Castro et al 2004;Teixeira & Machado 2004a, 2004bRossi et al 2005;Pereira et al 2006;Mendonça & Anjos 2006;Virillo et al 2007, Fonseca et al 2008. To increase understanding of the heterostyly system in the cerrado, this study aimed to investigate the phenology, distylous features, reproductive biology and fl oral visitors of Psychotria goyazensis Mull.…”