Thermal reaction norms of a subtropical and a tropical species of Diaphanosoma (cladocera) explain their distribution

Abstract

Species distribution boundaries are often associated with aspects of climate and modified by competitive interactions. In the tropical region, Diaphanosoma is the most diverse genus of Cladocera. Diaphanosoma dubium is widely distributed in China, whereas the tropical Diaphanosoma excisum is restricted to the islands off the south China coast. The mean temperature of the coldest month at the northern limit of its distribution is 15°C. We studied the effect of temperature (10–40°C) on life history traits of clones from 16 populations of D. dubium and D. excisum in life‐table experiments in order to determine if their thermal performance curves (TPCs) explain their distribution and to estimate the extent and mode of genetic variation in their TPCs. Our results show that both species have higher optimum temperatures (To ∼ 33°C), critical thermal minimum (CTmin = 10–15°C), and maximum (CTmax = 39–40°C) than temperate cladocerans. Clones of D. excisum had narrower TPCs and higher To than D. dubium clones, in accordance with predictions based on changes of temperature distributions with latitude. Significant levels of genetic variation in TPCs were present in both species. D. excisum had higher fitness than D. dubium at all temperatures above 15°C. However, at 15°C and below, D. dubium fitness was higher. Negative r at 15°C and below in combination with competition with the more cold‐adapted D. dubium exclude D. excisum from mainland China. TPCs of interacting species may be the basis of predicting future species distributions as temperature increases change the balance of biotic interactions.

Planktivorous fish predation masks anthropogenic disturbances on decadal trends in zooplankton biomass and body size structure in Lake Biwa, Japan

“…are thermophilic species (Lazareva 2012;Lazareva and Bolotov 2013), exhibiting a short generation time, large clutch size, and consequently a large intrinsic rate of increase at temperatures between 23 C and 29 C (Han et al 2011). Pajk et al (2018) also showed that intrinsic rates of increase in Diaphanosoma clones collected from southern China (20-28 N) were quite low below 20 C and optimum at 3 C. Usually, surface water temperatures rapidly increased in June every year in Lake Biwa (Kagami et al 2006). Average water temperature within the mixed layer, that is, above 20 m, exceeded 20 C from July to October, and high biomass of this species was mostly recorded during those months ( Fig.…”

Temperature niche difference and interspecific competition determine the parapatric distribution of two congeneric species in Diaphanosoma

“…D. excisum (clone D) was collected from Hedi reservoir, Zhanjiang, China (N21°85', E110°31'). The two clones chosen were each the best performing clone of its species from our previous life history experiments with 16 Diaphanosoma clones [25]. We measured their life history traits (net reproductive rate (R 0 ), intrinsic rate of population increase (r)) under a temperature range from 10°C to 40°C.…”

“…We measured their life history traits (net reproductive rate (R 0 ), intrinsic rate of population increase (r)) under a temperature range from 10°C to 40°C. 40℃ was estimated to be above the critical thermal maximum (CT max ), while 10℃was estimated to be below the critical thermal minimum (CT min ) [25]. Life table experiments were conducted at 15, 20, 25, 30, 34, and 38 °C.…”

“…The mean temperature of the coldest month (January) at the northern limit of the distribution of D. excisum in this region is about 15 °C, while the northward limits of D. dubium reaches the lower Amur river [21]. Pajk et al [25] measured the life history traits of clones from 16 populations of D. dubium and D. excisum under a large temperature range from 10 °C to 40 °C, and showed the tropical D. excisum had narrower thermal performance curves (TPCs) and higher optimum temperature than the subtropical D. dubium, but failed to reproduce at ≤ 15 °C. The authors concluded that negative r below 15 °C in combination with competition from the cold-adapted D. dubium limited northward distribution of D. excisum.…”

How planktonic microcrustaceans respond to environment and affect ecosystem: a functional trait perspective

“…The effects of temperature on biological processes are usually summarized in a thermal performance curve (Schulte et al 2011), and when temperatures are too high, thermal stress prevents growth and reproduction of organisms. Understanding thermal tolerance curves and ecological interactions has important implications for predicting geographical distributions of species in face of global climate change (Pajk et al 2018).…”