Abstract:Because most species in an ecological assemblage are rare, much of the species richness we value is due to taxa with few individuals or a restricted distribution. It has been apparent since the time of ecological pioneers such as Bates and Darwin that tropical systems have disproportionately large numbers of rare species, yet the distribution and abundance patterns of these species remain largely unknown. Here, we examine the diversity of freshwater fish in a series of lakes in the Amazonian várzea, and relate… Show more
“…Tropical freshwaters harbor a high proportion of narrowly distributed fish species and in poorly inventoried regions like Gabon such species may long go undetected (Pelayo-Villamil et al 2014). We have too few data to infer whether these two Cryptomyrus species are rare throughout their range, or simply rare where ichthyologists have chosen to collect (Hercos et al 2012). Because of the “commonness of rarity” in the tropics, description of singletons remains a common taxonomic practice (Lim et al 2012).…”
We use mitochondrial and nuclear sequence data to show that three weakly electric mormyrid fish specimens collected at three widely separated localities in Gabon, Africa over a 13-year period represent an unrecognized lineage within the subfamily Mormyrinae and determine its phylogenetic position with respect to other taxa. We describe these three specimens as a new genus containing two new species. Cryptomyrus, new genus, is readily distinguished from all other mormyrid genera by a combination of features of squamation, morphometrics, and dental attributes. Cryptomyrus ogoouensis, new species, is differentiated from its single congener, Cryptomyrus ona, new species, by the possession of an anal-fin origin located well in advance of the dorsal fin, a narrow caudal peduncle and caudal-fin lobes nearly as long as the peduncle. In C. ona, the anal-fin origin is located only slightly in advance of the dorsal fin, the caudal peduncle is deep and the caudal-fin lobes considerably shorter than the peduncle. Continued discovery of new taxa within the "Lower Guinea Clade" of Mormyridae highlights the incompleteness of our knowledge of fish diversity in West-Central Africa. We present a revised key to the mormyrid genera of Lower Guinea.
RESEARCH ARTICLE
Launched to accelerate biodiversity research
A peer-reviewed open-access journalJohn P. Sullivan et al. / ZooKeys 561: 117-150 (2016) 118 Résumé Nous avons démontré avec des marqueurs mitochondriaux et nucléaires que trois spécimens de poissons mormyridés faiblement électriques, collectés à trois localités au Gabon sur une période de 13 ans, forment une lignée inconnue au sein de la sous famille des Mormyrinae dont nous avons déterminé la position phylogénétique. Nous décrivons un nouveau genre et deux nouvelles espèces pour ces trois spécimens. Cryptomyrus, nouveau genre, se distingue des autres genres de mormyridés par une combinaison de caractères de l'écaillure, morphométriques, et dentaires. Cryptomyrus ogoouensis, nouvelle espèce, se distingue de sa seule espèce congénérique par sa nageoire anale qui commence nettement en avant de sa nageoire dorsale, son pédoncule caudal gracile et les lobes de sa nageoire caudale pratiquement aussi longs que son pédoncule caudal. Chez Cryptomyrus ona, nouvelle espèce, la nageoire anale commence légèrement en avant de l'origine de la nageoire dorsale, le pédoncule caudal est large, et les lobes de la nageoire caudale sont plus courts que le pédoncule caudal. La découverte ininterrompue de nouveaux taxa dans le «clade de basse Guinée» des Mormyridae illustre notre connaissance incomplète de la diversité des poissons de l'ouest de l'Afrique centrale. Nous présentons une clé révisée des genres de Mormyridae de basse Guinée.
“…Tropical freshwaters harbor a high proportion of narrowly distributed fish species and in poorly inventoried regions like Gabon such species may long go undetected (Pelayo-Villamil et al 2014). We have too few data to infer whether these two Cryptomyrus species are rare throughout their range, or simply rare where ichthyologists have chosen to collect (Hercos et al 2012). Because of the “commonness of rarity” in the tropics, description of singletons remains a common taxonomic practice (Lim et al 2012).…”
We use mitochondrial and nuclear sequence data to show that three weakly electric mormyrid fish specimens collected at three widely separated localities in Gabon, Africa over a 13-year period represent an unrecognized lineage within the subfamily Mormyrinae and determine its phylogenetic position with respect to other taxa. We describe these three specimens as a new genus containing two new species. Cryptomyrus, new genus, is readily distinguished from all other mormyrid genera by a combination of features of squamation, morphometrics, and dental attributes. Cryptomyrus ogoouensis, new species, is differentiated from its single congener, Cryptomyrus ona, new species, by the possession of an anal-fin origin located well in advance of the dorsal fin, a narrow caudal peduncle and caudal-fin lobes nearly as long as the peduncle. In C. ona, the anal-fin origin is located only slightly in advance of the dorsal fin, the caudal peduncle is deep and the caudal-fin lobes considerably shorter than the peduncle. Continued discovery of new taxa within the "Lower Guinea Clade" of Mormyridae highlights the incompleteness of our knowledge of fish diversity in West-Central Africa. We present a revised key to the mormyrid genera of Lower Guinea.
RESEARCH ARTICLE
Launched to accelerate biodiversity research
A peer-reviewed open-access journalJohn P. Sullivan et al. / ZooKeys 561: 117-150 (2016) 118 Résumé Nous avons démontré avec des marqueurs mitochondriaux et nucléaires que trois spécimens de poissons mormyridés faiblement électriques, collectés à trois localités au Gabon sur une période de 13 ans, forment une lignée inconnue au sein de la sous famille des Mormyrinae dont nous avons déterminé la position phylogénétique. Nous décrivons un nouveau genre et deux nouvelles espèces pour ces trois spécimens. Cryptomyrus, nouveau genre, se distingue des autres genres de mormyridés par une combinaison de caractères de l'écaillure, morphométriques, et dentaires. Cryptomyrus ogoouensis, nouvelle espèce, se distingue de sa seule espèce congénérique par sa nageoire anale qui commence nettement en avant de sa nageoire dorsale, son pédoncule caudal gracile et les lobes de sa nageoire caudale pratiquement aussi longs que son pédoncule caudal. Chez Cryptomyrus ona, nouvelle espèce, la nageoire anale commence légèrement en avant de l'origine de la nageoire dorsale, le pédoncule caudal est large, et les lobes de la nageoire caudale sont plus courts que le pédoncule caudal. La découverte ininterrompue de nouveaux taxa dans le «clade de basse Guinée» des Mormyridae illustre notre connaissance incomplète de la diversité des poissons de l'ouest de l'Afrique centrale. Nous présentons une clé révisée des genres de Mormyridae de basse Guinée.
“…Any community process that enables more numerically abundant taxa to persist (regardless of their size class) will increase evenness. Using data from a diverse Amazonian fish assemblage [14], we test the specific hypothesis that a biologically plausible mechanism for this is when large-bodied species become numerically abundant. Figure 1.( a , b ) The relationship between log numerical abundance and log body size in Tacaca pool and Juruá Grande lake, respectively.…”
Evenness is a key measure of community structure. Here, we examine the relationship between evenness and size–abundance distributions for both individuals and species using data gathered from Amazonian fish assemblages. We show that evenness increases as the fraction of numerically abundant species in larger body-size classes rises. As any processes that enable larger bodied species to increase their numerical dominance will influence evenness, these results help explain why evenness is an important correlate of ecosystem function.
“…An example from our study involves two aroid species (Philodendron billietiae and Philodendrum solimoesensis) which are very abundant in igapó, but which had only few individuals registered in várzea. Distinguishing species that are rare in all their distribution from species that are locally rare is fundamental for ecological studies that aim to assist conservation (Hercos et al 2012). …”
Research focusing on assemblages of vascular epiphytes in the Amazon are scarce. Th is is especially true for Amazonian fl oodplain forests, for which only two previous studies have been published. We compared composition, richness and structure of epiphyte assemblages in white-water and black-water fl oodplains (várzea and igapó) in Central Amazonia in order to close knowledge gaps concerning the distribution and richness of epiphytes. We established sixteen 25x25 m plots in each forest type, and counted and identifi ed all species of vascular epiphytes occurring on trees with a diameter at breast height (DBH) ≥10 cm. We observed a clear distinction in epiphytic species composition (r 2 =0.83, p=0.001) and diversity (t=3.24, P=0.003) between the two environments, with 61.5 % of species being restricted to várzea, 22.9 % restricted to igapó and only 15.6 % common to both ecosystems. Th e fl oodplains were also structurally diff erent for the most abundant species and those with the highest Epiphytic Importance Value (IVe). Th e diversity of trees did not infl uence the epiphyte diversity in either ecosystem. Th e forests were found to diff er in the composition, diversity and structure of their epiphytic assemblages, which must be taken into account when designing conservation action plans for these ecosystems and for their vascular epiphytes.
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