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Long-term competitive dynamics of two cryptic rotifer species: diapause and fluctuating conditions.

Gabaldón C, Carmona MJ, Montero-Pau J, Serra M - PLoS ONE (2015)

Bottom Line: They have a complex life cycle in which cyclical parthenogenesis occurs with diapausing stages being the result of sexual reproduction.We demonstrated that these species do not coexist under constant-salinity environment, as the outcome of competition is affected by the level of salinity-at low salinity, B. plicatilis excluded B. manjavacas, and the opposite outcome occurred at high salinity.Stable coexistence was not found in our system, which suggests that other factors or other salinity fluctuation patterns might act as stabilizing processes in the wild.

View Article: PubMed Central - PubMed

Affiliation: Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Valencia, Spain.

ABSTRACT
Life-history traits may have an important role in promoting species coexistence. However, the complexity of certain life cycles makes it difficult to draw conclusions about the conditions for coexistence or exclusion based on the study of short-term competitive dynamics. Brachionus plicatilis and B. manjavacasare two cryptic rotifer species co-occurring in many lakes on the Iberian Peninsula. They have a complex life cycle in which cyclical parthenogenesis occurs with diapausing stages being the result of sexual reproduction. B. plicatilis and B. manjavacasare identical in morphology and size, their biotic niches are broadly overlapping, and they have similar competitive abilities. However, the species differ in life-history traits involving sexual reproduction and diapause, and respond differently to salinity and temperature. As in the case of certain other species that are extremely similar in morphology, a fluctuating environment are considered to be important for their coexistence. We studied the long-term competitive dynamics of B. plicatilis and B. manjavacas under different salinity regimes (constant and fluctuating). Moreover, we focused on the dynamics of the diapausing egg bank to explore how the outcome of the entire life cycle of these rotifers can work to mediate stable coexistence. We demonstrated that these species do not coexist under constant-salinity environment, as the outcome of competition is affected by the level of salinity-at low salinity, B. plicatilis excluded B. manjavacas, and the opposite outcome occurred at high salinity. Competitive dynamics under fluctuating salinity showed that the dominance of one species over the other also tended to fluctuate. The duration of co-occurrence of these species was favoured by salinity fluctuation and perhaps by the existence of a diapausing egg bank. Stable coexistence was not found in our system, which suggests that other factors or other salinity fluctuation patterns might act as stabilizing processes in the wild.

No MeSH data available.


Related in: MedlinePlus

B. plicatilis diapausing egg ratio in the egg bank harvested after each growing season in Experiment 2.Rotifer populations were grown under a 10–40 g/L alternating salinity regime in two conditions (A) without diapausing egg bank and (B) with diapausing egg bank. Vertical bars are ± SE.
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pone.0124406.g003: B. plicatilis diapausing egg ratio in the egg bank harvested after each growing season in Experiment 2.Rotifer populations were grown under a 10–40 g/L alternating salinity regime in two conditions (A) without diapausing egg bank and (B) with diapausing egg bank. Vertical bars are ± SE.

Mentions: In Experiment 2, the diapausing egg number averaged 5,717 per growing season and replicate (n = 24; range: 197–17,457) (Fig 1). A total of 2,601 diapausing eggs were identified by molecular methods as B. plicatilis or B. manjavacas, and an average of four cycles per replicate were followed. The population densities were noticeably higher. No anomalies (e.g., a lack of diapausing egg production) occurred. Fig 3 shows the proportion of B. plicatilis in the diapausing eggs after each growing season in response to a fluctuating salinity regime in the two conditions tested (with and without a diapausing egg bank). B. plicatilis was excluded by B. manjavacas in all replicates of both conditions. However, in one of the replicates of the condition “with diapausing egg bank” B. plicatilis was able to recover—62 diapausing eggs were observed—in the third growing season, which corresponded to one of the low salinity periods (10 g/L) within the alternating salinity regime.


Long-term competitive dynamics of two cryptic rotifer species: diapause and fluctuating conditions.

Gabaldón C, Carmona MJ, Montero-Pau J, Serra M - PLoS ONE (2015)

B. plicatilis diapausing egg ratio in the egg bank harvested after each growing season in Experiment 2.Rotifer populations were grown under a 10–40 g/L alternating salinity regime in two conditions (A) without diapausing egg bank and (B) with diapausing egg bank. Vertical bars are ± SE.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400162&req=5

pone.0124406.g003: B. plicatilis diapausing egg ratio in the egg bank harvested after each growing season in Experiment 2.Rotifer populations were grown under a 10–40 g/L alternating salinity regime in two conditions (A) without diapausing egg bank and (B) with diapausing egg bank. Vertical bars are ± SE.
Mentions: In Experiment 2, the diapausing egg number averaged 5,717 per growing season and replicate (n = 24; range: 197–17,457) (Fig 1). A total of 2,601 diapausing eggs were identified by molecular methods as B. plicatilis or B. manjavacas, and an average of four cycles per replicate were followed. The population densities were noticeably higher. No anomalies (e.g., a lack of diapausing egg production) occurred. Fig 3 shows the proportion of B. plicatilis in the diapausing eggs after each growing season in response to a fluctuating salinity regime in the two conditions tested (with and without a diapausing egg bank). B. plicatilis was excluded by B. manjavacas in all replicates of both conditions. However, in one of the replicates of the condition “with diapausing egg bank” B. plicatilis was able to recover—62 diapausing eggs were observed—in the third growing season, which corresponded to one of the low salinity periods (10 g/L) within the alternating salinity regime.

Bottom Line: They have a complex life cycle in which cyclical parthenogenesis occurs with diapausing stages being the result of sexual reproduction.We demonstrated that these species do not coexist under constant-salinity environment, as the outcome of competition is affected by the level of salinity-at low salinity, B. plicatilis excluded B. manjavacas, and the opposite outcome occurred at high salinity.Stable coexistence was not found in our system, which suggests that other factors or other salinity fluctuation patterns might act as stabilizing processes in the wild.

View Article: PubMed Central - PubMed

Affiliation: Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Valencia, Spain.

ABSTRACT
Life-history traits may have an important role in promoting species coexistence. However, the complexity of certain life cycles makes it difficult to draw conclusions about the conditions for coexistence or exclusion based on the study of short-term competitive dynamics. Brachionus plicatilis and B. manjavacasare two cryptic rotifer species co-occurring in many lakes on the Iberian Peninsula. They have a complex life cycle in which cyclical parthenogenesis occurs with diapausing stages being the result of sexual reproduction. B. plicatilis and B. manjavacasare identical in morphology and size, their biotic niches are broadly overlapping, and they have similar competitive abilities. However, the species differ in life-history traits involving sexual reproduction and diapause, and respond differently to salinity and temperature. As in the case of certain other species that are extremely similar in morphology, a fluctuating environment are considered to be important for their coexistence. We studied the long-term competitive dynamics of B. plicatilis and B. manjavacas under different salinity regimes (constant and fluctuating). Moreover, we focused on the dynamics of the diapausing egg bank to explore how the outcome of the entire life cycle of these rotifers can work to mediate stable coexistence. We demonstrated that these species do not coexist under constant-salinity environment, as the outcome of competition is affected by the level of salinity-at low salinity, B. plicatilis excluded B. manjavacas, and the opposite outcome occurred at high salinity. Competitive dynamics under fluctuating salinity showed that the dominance of one species over the other also tended to fluctuate. The duration of co-occurrence of these species was favoured by salinity fluctuation and perhaps by the existence of a diapausing egg bank. Stable coexistence was not found in our system, which suggests that other factors or other salinity fluctuation patterns might act as stabilizing processes in the wild.

No MeSH data available.


Related in: MedlinePlus