Seasonality dictates changes in the ecological interactions among spatial dominants
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ORIGINAL PAPER
Seasonality dictates changes in the ecological interactions among spatial dominants Marianela Gastaldi1 · Fausto Nahuel Firstater1,2,3 · María Alejandra Romero1,2,3 · Patricio Javier Pereyra1,2,3 · Maite Andrea Narvarte1,2,3 Received: 15 April 2020 / Accepted: 15 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Marine coasts are dynamic environments where spatial-physical gradients interact with seasonality. In the Patagonia in particular, high temperatures and strong winds lead to stressing physical conditions that shape intertidal communities. In a previous study, we found that the interaction between the sponge Hymeniacidon perlevis and the macroalga Ulva lactuca was context-dependent, switching from positive at the harsher intertidal to negative at the milder subtidal environment. Temporal variation in the physical variables, however, may also affect species performance and interaction strength. Since Patagonian shores are strongly seasonal environments, we evaluated how the interactions (competitive or cooperative) among these two spatially dominant species changed over a temporal-stress gradient throughout a year. We predicted that the macroalga would facilitate the sponge in seasons with more severe environmental conditions, whereas negative or neutral interactions would prevail when environmental conditions were milder. Our results demonstrated that the sign and intensity of the interaction between Hymeniacidon and Ulva changed over the seasons and coincided with a hump-shaped model, involving a neutral interaction in the milder seasons of autumn and winter, then switching to a positive one in the inclement springtime, and finally shifting to a negative relationship in the harshness of the summer. The amelioration of stressful conditions through shading did not satisfactorily explain the underlying mechanism for this varying interaction, an aspect that still remains unclear. Nevertheless, several mechanisms are discussed both within the context of the stress gradient hypothesis and the specific physiological constraints of intertidal organisms.
Introduction
Responsible Editor: F. Bulleri. Reviewed by: G.M. Martins and undisclosed experts. * Marianela Gastaldi [email protected] 1
Departamento de Biología, Escuela Superior de Ciencias Marinas, Universidad Nacional del Comahue, San Martín 247, 8520 San Antonio Oeste, Río Negro, República Argentina
2
Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos Almirante Storni, Güemes, 1030 San Antonio Oeste, República Argentina
3
Consejo Nacional de Investigaciones Científicas y Técnicas, Godoy Cruz, 2290 Ciudad Autónoma de Buenos Aires, República Argentina
One of the central goals of ecology is to understand the structure of natural communities and the processes that shape them. The stress gradient hypothesis states that the relative impact of processes structuring a community depends on the biotic and abiotic environmental conditions, predicting that ne
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