Saturday, April 9, 2016

[Invertebrate / Evolution • 2016] Pattern of Co-Occurrence Between Ant-Mimicking Jumping Spiders and Sympatric Ants in A Bornean Tropical Rainforest

Fig. 1. Dorsal views of the model ants and their ant-mimicking spiders, showing the body parts removed legs and antennae.
A, Camponotus saundersi; B, Myrmarachne alticephalon;
 C, Polyrhachis olybia; D, Myrmarachne maxillosa;
E, Polyrhachis boltoni; F, Polyrhachis phalerata; G. Myrmarachne malayana.

To evaluate the pattern of co-occurrence between ant-mimicking jumping spiders and sympatric ants in a tropical rainforest, we sampled these arthropods and also non-mimicking jumping spiders by net-sweeping from the understory vegetation in Sabah, Malaysian Borneo. We collected the spiders and ants from a total of 594 sample points, with ants occurring in 445 points (79.4%), non-mimicking jumping spiders in 308 (51.9%), Agorius ant-mimicking spiders in 40 (6.7%), and Myrmarachne ant-mimicking spiders in 59 (9.9%). Frequencies of occurrence of non-mimicking jumping spiders showed no significant difference in relation to ant-occurrence, whereas both of the ant-mimicking spider genera occurred significantly more frequently with ants. Agorius spiders co-occurred with a wider variety of different ant genera, compared to Myrmarachne, but logistic regression analyses and a null model test showed no specific associations between Agorius spiders and the sympatric ant genera. The mimetic resemblances of Agorius spiders are considered to be much less ant-like than those of Myrmarachne spiders, because their constriction of the cephalothorax is not as obvious as in Myrmarachne. These data provide support for the multi-model hypothesis (Edmunds 2000), which predicted that a poor ant-mimic should occur in ranges of many different ants, compared to good ant-mimic.

Key words. Ant-mimicry, Formicidae, Salticidae, Co-occurrence relationship, Multi-model hypothesis, Southeast Asian tropics

Yoshiaki Hashimoto, Tomoji Endo, Takao Itioka, Fujio Hyodo, Takashi Yamasaki and Maryati Mohamed. 2016. Pattern of Co-Occurrence Between Ant-Mimicking Jumping Spiders and Sympatric Ants in A Bornean Tropical Rainforest. RAFFLES BULLETIN OF ZOOLOGY. 64: 70–75.