Difference between revisions of "Geonoma maxima"

Taxonomic notes: - Geonoma maxima is a member of the G. macrostachys clade, differing from all other species in its locular epidermis without an operculum. It also has more branched inflorescences (4-50 rachillae) compared to the rest of the clade (1-9 rachillae). It is another variable species which has been treated differently by Wessels Boer (1968) and Henderson et al. (1995). Unlike other species complexes, for example G. macrostachys, G. maxima exhibits rather well-defined geographic disjunction and morphological variation, allowing for recognition of various subspecies, as explained below. (Henderson, A.J. 2011)/Palmweb.

Subspecific variation: - Four traits vary within this species (stem branching, leaf division, leaf plication, pistillate flower persistence). There are very few data for stem branching, and this and leaf division are excluded from the following analyses. Leaf plication and pistillate flower persistence divide the specimens into three groups. However, leaf plication is difficult to score in this species and specimens with persistent pistillate flowers may be of hybrid origin (see below). Furthermore, there is no geographic separation between these groups. Geonoma maxima is widespread across the Amazon region, and there are isolated populations in the Magdalena valley and Pacific coast of Colombia and eastern Andean slopes in Venezuela. Apart from traits, one attribute (leaf division) divides the specimens into two groups. Leaves of one group are regularly pinnate and the pinnae (at least those from the middle part of the leaf) have several main veins, usually three to five. In the second group, all specimens have either undivided leaves, irregularly pinnate leaves (sometimes with 1-veined pinnae present), or leaves with 1-veined pinnae (at least those from the middle part of the leaf). The first group - with regularly pinnate leaves with 3-5-veined pinnae - can be divided into four separate subgroups based partly on geography and partly on variables. ANOVA shows that for pair wise comparison probabilities, 18 variables (plant height, stem diameter, internode length, petiole length, rachis length, rachis width, basal pinna length, basal pinna width, apical pinna length, apical pinna angle, prophyll length, interbract distance, peduncle length, peduncle width, rachilla length, rachilla width, number of rachillae, fruit diameter) differ significantly (P <0.05) between at least one pair of subgroups, although no variable differs amongst all four subgroups. Based on these results and geography, these four subgroups are recognized as subspecies (subspp. hexasticha, maxima, multiramosa, sigmoidea). The second group - with leaves undivided, irregularly pinnate (sometimes with 1-veined pinnae present), or regularly pinnate with 1-veined pinnae - can be divided into six separate subgroups based partly on geography, partly on variables, and on one trait (leaf plication). ANOVA shows that for pair wise comparison probabilities, 22 variables (plant height, stem diameter, leaf number, petiole length, rachis length, rachis width, number of pinnae, basal pinna length, basal pinna width, basal pinna angle, apical pinna length, apical pinna width, apical pinna angle, prophyll length, interbract distance, peduncle length, peduncle width, rachilla length, rachilla width, number of rachillae, fruit length, fruit diameter) differ significantly (P <0.05) between at least one pair of subgroups, although no variable differs amongst all six subgroups. Based on these results and geography, these six subgroups are recognized as subspecies (subspp. ambigua, chelidonura, camptoneura, compta, dispersa, spixiana). (Henderson, A.J. 2011)/Palmweb. Editing by edric.