Investigating the floral and reproductive biology of the endangered microendemic cactus Uebelmannia buiningii Donald (Minas Gerais, Brazil)

Abstract

The Cactaceae are known to be amongst the most endangered plant families of the world due to reduction of their habitats and activities of collectors. As the species of the family are dependent on animals to perform cross pollination, and hence seed production, their population performance may be further negatively affected by interrupted biotic interactions. For efficient conservation of rare species, knowledge on reproductive biology and pollinators is of prime importance. In our study we focused on Uebelmannia buiningii Donald, a microendemic cactus from the Serra Negra State Park, Minas Gerais state, Brazil. During four field expeditions to three localities of the species between September 2012 and September 2013, we measured flowers, detected nectar-guides and osmophores and performed pollen viability tests. We studied the reproductive system of the species using manual self-and cross-pollination tests and observed pollinators. Our results revealed that the flowering period takes place during the dry season, between April and October, and that the diurnal flowers open between 7:00 a.m. and 5 p.m. The flowers are shortly tubular with yellow perianth-segments. We found neither nectar nor nectar-guides, and osmophores appeared as glands within the flower tube. Whereas pollen viability was 90.25%, manual crosspollination tests have shown cross-pollination with gametophytic incompatibility. We observed two bee species visiting the flowers and acting as effective pollinators: Dialictus opacus and Plebeia sp. The combination of low reproductive activity with gametophytic incompatibility, together with the reduced number of individuals in a population and low number of populations, makes the endemic cactus U. buiningii a critically endangered species.

Pollen‐feeding bees in Uebelmannia pectinifera subsp. pectinifera – reproductive biology of an endemic cactus from the campo rupestre of eastern Brazil

“…Floral characters of Uebelmannia , in general, presents melittophily syndrome and this has already been reported in Schulz and Machado (2000). The same traits were observed in a study with U. buiningii (Teixeira et al 2018).…”

“…The naturally fragmented distribution of these taxon (Taylor and Zappi 2004, Zappi and Taylor 2008, Teixeira et al 2018), together with the reduction of their habitat due to anthropogenic pressures (e.g. mining for precious and semi‐precious stones and quartz sand and targeted collection of individuals by cactus amateurs) have led to their categorization both in the Brazilian Red Book for plants (Martinelli and Moraes 2013) and by IUCN (2020) as CR for U. buiningii , VU for U. gummifera and EN for U. pectinifera .…”

“…Only 10% of the 270 Brazilian cacti have been studied from the floral and reproductive biology (Schlindwein and Wittmann 1995, Aona et al 2006, Colaço et al 2006, Lenzi and Orth 2011, Rego et al 2012, Gomes et al 2014, Martins et al 2016, Paulino‐Neto et al 2016, Martins and Freitas 2018, Rocha et al 2019). Teixeira et al (2018) inferred that Uebelmannia buiningii may be Critically Endangered (CR) because of a combination of pressure on its habitat and illegal collection negatively impacting its already small populations, added to gametophyte self‐incompatibility that leads to obligate allogamy, dependent on pollinators in order to produce seeds.…”

Pollination biology of the endangered columnar cactus Cipocereus crassisepalus: a case of close relationship between plant and pollinator

“…2011), but pollination modes, not only of columnar cacti but of the family as a whole, are little known. Studies of reproductive and floral biology of cacti have examined only about 5% of the species recorded for the country (Teixeira et al . 2018).…”

Fiber‐optic refractometer for in vivo sugar concentration measurements of low‐nectar‐producing flowers

“…Phillips et al, 2018;Takkis et al, 2018), conservation of endangered species (e.g. Montagna et al, 2018;Teixeira et al, 2018) and enhancement in food production (e.g. Prasifka et al, 2018;Soto et al, 2018).…”