Morphological and metabolic variations among Corbicula lineages in Argentina and potential distribution implications

LEANDRO HÜNICKEN; FRANCISCO SYLVESTER; ESTEBAN MARCELO PAOLUCCI

Luján

Congreso; VIII Congreso Argentino de Limnología; 2018

Universidad Nacional de Luján

Within biological communities, energy serves as a central commodity that contributes to shape up overall geographic patterns of species´ abundances and distribution. Closely related species that are contemporaneously introduced in the same area, often soon develop segregated distribution ranges. During the second half of the past century, two lineages of Corbicula Asian clams (Forms A/R, widely known as C. fluminea, and C/S C. largillierti) colonized the Río de la Plata estuary, and from there achieved widespread distribution in Argentina. While C. fluminea dominated in the estuary and main rivers to the east and south of the country, C. largillierti prevailed in higher order rivers, streams, and lakes in central and northwest regions. To explore possible causes of these distributions, we compare the morphology and basal metabolic rates (BMR) of five invasive Corbicula populations belonging to the two lineages. We conducted oxygen consumption experiments in respiration chambers to calculate BMR; and measured the gill area (GA), valve volume (VV), ash-free dry weight (AFDW), and filament density (FD). We calculated the weight relative gill area (RGA) as the ratio between GA and AFDW, and used GLMs to explore the relationships between morphological variables and BMR. We found a strong positive correlation between RGA and BMR (R141= 0.78, p< 0.001). C. fluminea showed significantly higher BMR (F1,141= -3.108, p= 0.001885) and lower FD (F1,140= 4.04, p< 0.001) than C. largillierti. Within lineages, C. fluminea clams from Punta Lara showed higher BMR (F1,56 = 6.453, p< 0.001) and mass gain (AFDW, F1,56= -2.928, p= 0.0049) than their Buenos Aires conspecifics, which might be associated with environmental conditions and anthropogenic impact. The morphological and metabolic differences between the lineages might affect mechanisms of niche differentiation, patterns of geographic dominance and replacement among forms.