Diploid male production in a rare and locally distributed bumblebee, Bombus florilegus (Hymenoptera, Apidae)

Abstract

The European bumblebee B. terrestris was recently introduced in Japan for agricultural purposes and has now become naturalized. The naturalization of this exotic species may have great detrimental effects on closely related native Japanese bumblebees. The Japanese bumblebee Bombus florilegus is a rare and locally distributed species found in the Nemuro Peninsula of Hokkaido, Japan. In order to assess its population genetics, we estimated the genetic structure of B. floriA C H T U N G T R E N N U N G legus in 16 breeding colonies (queen, workers, and males) and 20 foraging queens by analyzing microsatellite DNA markers. Of the 36 queens analyzed by genotyping and dissection, 32 had been inseminated by a male. The remaining 4 had not been inseminated at all. Of the 4 nonmated queens, one was triploid. Diploid males were found in 4 breeding colonies. Based on the microsatellite data, it appears that B. florilegus has low reproductive success. Since matched mating and nonmating within local populations are high, the extinction risk is correspondingly higher. Our results suggest that conservation of the Japanese B. florilegus is required in order to protect it from both habitat destruction and the naturalization of alien species.

Discrimination of haploid and diploid males of Bombus terrestris (Hymenoptera; Apidae) based on wing shape

“…Some studies have tried to quantify the presence of diploid males in wild populations. In Japanese Bombus florilegus , 28 % of the males were diploid (Takahashi et al 2008), whereas diploid males were also frequent in fragmented populations of British Bombus muscorum . Because diploid male production occurs under conditions of severe inbreeding, the presence of diploid males can be used as an indicator for population (or colony) health and can be used to assess the viability of bee populations (Zayed et al 2004).…”

“…As a consequence, the colony produces only half the normal quantity of workers from the start and thus will remain rather small in size, with low production of new queens. Second, as most bumble bee species are monandrous (even known polyandrous species mate with a frequency close to one; Estoup et al 1996;Payne et al 2003;Takahashi et al 2008) and diploid males produce diploid sperm, queens mating with diploid males produce 100 % of sterile triploid offspring leading to the inbred strain having much lower fitness than outbred colonies. In wild populations, this is known as the Bdiploid male extinction vortex^ (Zayed and Packer 2005).…”

Diploid males, diploid sperm production, and triploid females in the ant Tapinoma erraticum

“…However, their ability to produce sperm, the ploidy level of sperm cells, and male capability to fertilize females under natural conditions remain poorly studied. Takahashi et al (2008) reported the occurrence of several diploid males and a single triploid, unmated female in native populations of the rare and endangered bumblebee Bombus florilegus. Two other genetic studies have dealt with populations of invasive species in their introduced range.…”

Kin recognition and inbreeding reluctance in bumblebees

“…In the Japanese bumblebee Bombus florilegus 28% of sampled colonies contained diploid males; similarly, in the UK, 5% of Bombus muscorum males were found to be diploid. In both cases this is thought to result from low genetic diversity, small population size and fragmentation (Takahashi et al, 2008;Darvill et al, 2006). Recent modelling has demonstrated that DMP can initiate a rapid extinction vortex (Zayed and Packer, 2005), which has implications for the persistence of small genetically impoverished populations of bumblebees.…”