When phylogenetically close, two competing species may reproductively interfere, and thereby affect their population dynamics. We tested for reproductive interference (RI) between two congeneric haplo-diploid spider mites, Tetranychus evansi and Tetranychus urticae, by investigating their interspecific mating and their population dynamics when they competed on the same plants. They are both pests of tomato, but differ in the host plant defences that they suppress or induce. To reduce the effect of plant-mediated interaction, we used a mutant tomato plant lacking jasmonate-mediated anti-herbivore defences in the competition experiment. In addition, to manipulate the effect of RI, we introduced founder females already mated with conspecific males in mild RI treatments or founder, virgin females in strong RI treatments (in either case together with heterospecific and conspecific males). As females show first-male sperm precedence, RI should occur especially in the founder generation under strong RI treatments. We found that T. urticae outcompeted T. evansi in mild, but not in strong RI treatments. Thus, T. evansi interfered reproductively with T. urticae. This result was supported by crossing experiments showing frequent interspecific copulations, strong postmating reproductive isolation and a preference of T. evansi males to mate with T. urticae (instead of conspecific) females, whereas T. urticae males preferred conspecific females. We conclude that interspecific mating comes at a cost due to asymmetric mate preferences of males. Because RI by T. evansi can improve its competitiveness to T. urticae, we propose that RI partly explains why T. evansi became invasive in Europe where T. urticae is endemic.
The number of pairs where intra- and inter-specific copulations occurred between Tetranychus urticae and T. evansi
Data sheet used in the statistic analyses of the number of pairs where intra- and inter-specific copulations occurred within 0.5 h after introduction of a virgin female and three virgin males onto a tomato leaf arena. "Experiment" shows the pair of crossing experiment: EE is T. evansi (♀) × T. evansi (♂), EU is T. evansi (♀) × T. urticae (♂), UU is T. urticae (♀) × T. urticae (♂), and UE is T. urticae (♀) × T. evansi (♂). "Female" and "Male" show female species and male species of the pair: E is T. evansi and U is T. urticae. "Yes" shows the number of pair where copulations occurred. "No" shows the number of pair where copulations did not occure. "Comb" shows the crossing type: "Intra" is intraspecific crossing and "Inter" is interspecific crossing.
CopF.txt
The duration of intra- and inter-specific copulations between Tetranychus urticae and T. evansi
Data sheet used in the analyses of the copulation duration in intra- and inter-specific crosses. "Name" shows the name of the pair. "Experiment" shows the pair of crossing experiment: EE is T. evansi (♀) × T. evansi (♂), EU is T. evansi (♀) × T. urticae (♂), UU is T. urticae (♀) × T. urticae (♂), and UE is T. urticae (♀) × T. evansi (♂). "Female" and "Male" show female species and male species of the pair: E is T. evansi and U is T. urticae. "1stCop" shows the duration of copulations. "Comb" shows the crossing type: "Intra" is intraspecific crossing and "Inter" is interspecific crossing.
CopT2.txt
The numbers of eggs oviposited by mothers and the numbers of daughters and sons brought up from the eggs in the intra- and inter-specific crossing between Tetranychus urticae and T. evansi.
Data sheet used in the analyses of the number of eggs, the juvenile survival rate of offspring and the female sex ratio among offsprings produced by females mated with con- or hetero-specific males or virgin females. "Name" shows the name of the pair. "Experiment" shows the pair of crossing experiment: EE is T. evansi (♀) × T. evansi (♂), EU is T. evansi (♀) × T. urticae (♂), UU is T. urticae (♀) × T. urticae (♂), UE is T. urticae (♀) × T. evansi (♂), U is virgin oviposition by T. urticae (♀) and E is virgin oviposition by T. evansi (♀). "Pfemale" shows the species of mother: E is T. evansi and U is T. urticae. "Comb" shows the crossing type: "Intra" is intraspecific crossing, "Inter" is interspecific crossing and "Unmated" is virgin oviposition. "Male" shows the number of sons. "Female" shows the number of daughters. "Deadlarva" is the number of offspring that died before developing to adult stage. "TotalEgg" shows the number of eggs oviposited by the mother.
CopR.txt
Population dynamics of Tetranychus urticae and T. evansi on tomato plants (def-1) over a period of 4 weeks after mite introduction
Data sheet used in the comparisons of the number of female mites on tomato plants over week among treatments. "Exp" shows the treatment: A is Strong RI, B is Control 1, C is Control 2, D is Mild RI, E is Control 3 and F is Control 4 in Table 1 in the paper. "PotNo" and "PotNo2" show the name or the number of the trials. "DifSp" shows species of the founder females: E is T. evansi and U is T. urticae. "Female" shows the reproductive status of the founder females, unmated or mated. "Week" shows the time when the number of mites was counted. "NO" shows the number of mites. "NO2" shows the number of mites per the number of founder females.
Pot2.txt
R script in the analysis of male choice test
ChoiceT.pdf