10:00 AM - 10:15 AM
[BCG07-05] Historical analysis of genetic diversity and determinants of establishment success in alien Daphnia of the ancient Lake Biwa: insights from sedimentary archives.
Keywords:sedimentary DNA, genetic diversity, zooplankton, alien species, Lake Biwa, biological interaction
Representing a recent paradigm shift in understanding genetic signals of environments and sedimentary archives, environmental DNA (eDNA) in sediments (hereafter, sedDNA) has been identified as a powerful tool for reconstructing past dynamics of organisms leaving no visible remains. Now sedDNA has attracted attention as a tool for reconstructing the historical population dynamics of various organisms. This study aims to clarify the invasion process of alien species and the factors controlling establishment success, considering a historical variation of genetic diversity. We report on the results conducted using microscopic and DNA analysis, focusing on zooplankton Daphnia in Lake Biwa, known as one of the ancient lakes.
Invasive species pose serious threats to global biodiversity, prompting studies to identify factors underlying invasion and establishment success. However, it’s difficult to discern the factors due to the lack of survey data since the initial invasion, because introduced species frequently remain unnoticed until their population becomes large enough. Here, we investigated the establishment process of the alien zooplankton, Daphnia pulicaria, in the past 30 years using sedimentary archives at Lake Biwa. We performed genetic analysis on mitochondrial DNA sequences of the control region and ND5 gene of ephippia in sediments, as well as present females from water samples. Furthermore, we investigated the relationships between the abundance of D. pulicaria and its major predator fish, Ayu, based on the catch data, in addition to its competitor, Daphnia galeata whose population abundance was estimated based on claw remains.
As a result, a total of 104 mtDNA control region sequences recovered from the ephippia collected from sediment cores, as well as from adult females in lake water, were identical even though the mtDNA control region is known for its high variability. This single haplotype detected in Lake Biwa was novel and was most closely related to the haplotypes detected in D. pulicaria populations from North America. Consistent with the finding, all the mtDNA ND5 sequences were ascribed to a single haplotype, which was closely related to the haplotypes found in North America. Further analysis showed the abundance of D. pulicaria was not correlated with that of a competitor but was negative with that of a predator.
These findings demonstrated that the alien D. pulicaria population in Lake Biwa originated from one genotype, possibly introduced from the North American region. Their successful establishment was primarily influenced by reduced fish predation pressure, with a limited impact from competitive interactions and potential hindrance for adaptation caused by loss of genetic variation. Enemy-free space might thus be very vulnerable to invasion by Daphnia.
References: Brede et al. (2009) PNAS 106: 4758-. Verschuren and Marnell (1997) Transactions of the American Fisheries Society 126:21-, Tsugeki et al. (2022) Scientific Reports 12:1741.
Invasive species pose serious threats to global biodiversity, prompting studies to identify factors underlying invasion and establishment success. However, it’s difficult to discern the factors due to the lack of survey data since the initial invasion, because introduced species frequently remain unnoticed until their population becomes large enough. Here, we investigated the establishment process of the alien zooplankton, Daphnia pulicaria, in the past 30 years using sedimentary archives at Lake Biwa. We performed genetic analysis on mitochondrial DNA sequences of the control region and ND5 gene of ephippia in sediments, as well as present females from water samples. Furthermore, we investigated the relationships between the abundance of D. pulicaria and its major predator fish, Ayu, based on the catch data, in addition to its competitor, Daphnia galeata whose population abundance was estimated based on claw remains.
As a result, a total of 104 mtDNA control region sequences recovered from the ephippia collected from sediment cores, as well as from adult females in lake water, were identical even though the mtDNA control region is known for its high variability. This single haplotype detected in Lake Biwa was novel and was most closely related to the haplotypes detected in D. pulicaria populations from North America. Consistent with the finding, all the mtDNA ND5 sequences were ascribed to a single haplotype, which was closely related to the haplotypes found in North America. Further analysis showed the abundance of D. pulicaria was not correlated with that of a competitor but was negative with that of a predator.
These findings demonstrated that the alien D. pulicaria population in Lake Biwa originated from one genotype, possibly introduced from the North American region. Their successful establishment was primarily influenced by reduced fish predation pressure, with a limited impact from competitive interactions and potential hindrance for adaptation caused by loss of genetic variation. Enemy-free space might thus be very vulnerable to invasion by Daphnia.
References: Brede et al. (2009) PNAS 106: 4758-. Verschuren and Marnell (1997) Transactions of the American Fisheries Society 126:21-, Tsugeki et al. (2022) Scientific Reports 12:1741.