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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 produced during each growing season in response to the salinity fluctuation regime in Experiment 1.(A) 10 g/L constant salinity (all growing seasons at 10 g/L); (B) 40 g/L constant salinity (all growing seasons at 40 g/L); (C) 10–40 g/L alternating salinity (the first growing season at 10 g/L followed by the second growing season at 40 g/L, and then again at 10 g/L, and so on); (D) 40–10 g/L alternating salinity (the same as (C) but starting at 40 g/L); and (E) 10 to 40 g/L increasing salinity (each growing season started at 10 g/L, but the salinity was gradually increased during the growing season until it reached 40 g/L). Vertical bars are ± SE.
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pone.0124406.g002: B. plicatilis diapausing egg ratio in the egg bank produced during each growing season in response to the salinity fluctuation regime in Experiment 1.(A) 10 g/L constant salinity (all growing seasons at 10 g/L); (B) 40 g/L constant salinity (all growing seasons at 40 g/L); (C) 10–40 g/L alternating salinity (the first growing season at 10 g/L followed by the second growing season at 40 g/L, and then again at 10 g/L, and so on); (D) 40–10 g/L alternating salinity (the same as (C) but starting at 40 g/L); and (E) 10 to 40 g/L increasing salinity (each growing season started at 10 g/L, but the salinity was gradually increased during the growing season until it reached 40 g/L). Vertical bars are ± SE.

Mentions: In Experiment 1, the diapausing egg number averaged 1870 per growing period and replicate (n = 50; range: 0–3,970) (Fig 1). The total number of diapausing eggs identified as B. plicatilis or B. manjavacas via molecular methods was 3,738. We followed an average of 3.27 cycles per replicate. This relatively low number of cycles was due primarily to the absence of one of the species in the diapausing eggs produced during two consecutive growing seasons. However, one of the replicates at 10–40 g/L alternating salinity was lost in its fourth cycle due to unknown causes after a 100% frequency of B. plicatilis frequency had been achieved, and another replicate maintained at the same conditions did not produce diapausing eggs. The proportion of B. plicatilis in the diapausing eggs produced after each growing season in response to the five salinity fluctuation regimes (Experiment 1) is shown in Fig 2. If the salinity regime was constant throughout the growing seasons, one of the species was excluded in all replicates in a consistent way. At a lower salinity, B. manjavacas was excluded; at a high salinity, B. plicatilis was excluded. B. plicatilis was also excluded under a fluctuating-salinity regime in which the salinity of the first growing season was high (40–10 g/L treatment).


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 produced during each growing season in response to the salinity fluctuation regime in Experiment 1.(A) 10 g/L constant salinity (all growing seasons at 10 g/L); (B) 40 g/L constant salinity (all growing seasons at 40 g/L); (C) 10–40 g/L alternating salinity (the first growing season at 10 g/L followed by the second growing season at 40 g/L, and then again at 10 g/L, and so on); (D) 40–10 g/L alternating salinity (the same as (C) but starting at 40 g/L); and (E) 10 to 40 g/L increasing salinity (each growing season started at 10 g/L, but the salinity was gradually increased during the growing season until it reached 40 g/L). Vertical bars are ± SE.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0124406.g002: B. plicatilis diapausing egg ratio in the egg bank produced during each growing season in response to the salinity fluctuation regime in Experiment 1.(A) 10 g/L constant salinity (all growing seasons at 10 g/L); (B) 40 g/L constant salinity (all growing seasons at 40 g/L); (C) 10–40 g/L alternating salinity (the first growing season at 10 g/L followed by the second growing season at 40 g/L, and then again at 10 g/L, and so on); (D) 40–10 g/L alternating salinity (the same as (C) but starting at 40 g/L); and (E) 10 to 40 g/L increasing salinity (each growing season started at 10 g/L, but the salinity was gradually increased during the growing season until it reached 40 g/L). Vertical bars are ± SE.
Mentions: In Experiment 1, the diapausing egg number averaged 1870 per growing period and replicate (n = 50; range: 0–3,970) (Fig 1). The total number of diapausing eggs identified as B. plicatilis or B. manjavacas via molecular methods was 3,738. We followed an average of 3.27 cycles per replicate. This relatively low number of cycles was due primarily to the absence of one of the species in the diapausing eggs produced during two consecutive growing seasons. However, one of the replicates at 10–40 g/L alternating salinity was lost in its fourth cycle due to unknown causes after a 100% frequency of B. plicatilis frequency had been achieved, and another replicate maintained at the same conditions did not produce diapausing eggs. The proportion of B. plicatilis in the diapausing eggs produced after each growing season in response to the five salinity fluctuation regimes (Experiment 1) is shown in Fig 2. If the salinity regime was constant throughout the growing seasons, one of the species was excluded in all replicates in a consistent way. At a lower salinity, B. manjavacas was excluded; at a high salinity, B. plicatilis was excluded. B. plicatilis was also excluded under a fluctuating-salinity regime in which the salinity of the first growing season was high (40–10 g/L treatment).

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