Evaluating the tradeoffs of a generalist parasitoid fungus, Ophiocordyceps unilateralis, on different sympatric ant hosts

Abstract

host's population and by genetic trade-offs in adaptation to different hosts. Thus, co-evolutionary consequence critically depends on the pervasiveness of genetic interactions. Ophiocordyceps unilateralis (Clavicipitaceae: Hypocreales), also referred to as a "zombie fungus, " is a fungal pathogen considered specific to ants of the tribe Camponotini (Formicinae: Formicidae). This entomopathogen currently found predominantly in tropical forest ecosystems 9. Due to the increased amount of research on Ophiocordyceps in recent years, the name O. unilateralis is often extended to O. unilateralis sensu lato, which suggests that there are several cryptic species within O. unilateralis, which are yet to be described 9. Studies have reported that O. unilateralis in the southern Thailand mainly parasitize carpenter ants, especially Camponotus leonardi, as principal hosts with minor supplementary infections found in some Polyrhachis ants 3,10. Evans et al. 11 found diversity within the complex in four different Camponotus species in Brazil and suggested that O. unilateralis seems to be a species complex of widespread distribution with noticeable local diversities of associated hosts. Subsequent papers dealing with new taxa and issues from Thailand, Japan, and Brazilian Amazon on both Camponotus and Polyrhachis hosts have provided evidence to support for the "one ant, one Ophiocordyceps species" hypothesis as raised by Evans et al. 11-15. Thus, O. unilateralis may have specificity toward different ant species, species delimitation, and host-parasite interaction leading to speciation. We herein report an O. unilateralis s.l. species that can sympatrically infect eight ant species, namely P.

Possible impacts of the predominant Bacillus bacteria on the Ophiocordyceps unilateralis s. l. in its infected ant cadavers

“…In the present study, we describe the bacterial communities in O. unilateralis s. l. -infected ant cadavers. Because the host range is wider in O. unilateralis s. l. from Taiwan 15 compared with related species 16 – 19 , bacterial communities were captured by a culture-dependent method from two infected ant species, a principal host, Polyrhachis moesta , and an alternate sympatric host, P. wolfi . We evaluate the biological properties and the possible impact of the predominant bacterial species on O. unilateralis s. l. infection and examine bacterial growth in relation to the production of naphthoquinone derivatives by O. unilateralis s. l. 10 – 12 .…”

Bacillus Thuringiensis Predominated in the Zombie Fungus Ophiocordyceps Unilateralis S. L.-Infected Ant Cadavers and Investigation of its Biological Properties

“…The accumulation of naphthoquinones might open a niche for B. thuringiensis isolates to out compete other saprophytes, but the lower bacterial diversity in the principal host suggests a more sophisticated manipulation of the physiological conditions of the principal host. Despite not diverging among its sympatric hosts, O. unilateralis s. l. displays higher infection performances in one ant species than in the other host species in Taiwan 15 . The e cient exploitation of host resources may result from better modi cation of host physiological conditions, which consequently causes a more uniform environment for speci c bacterial species.…”

“…Ants on the leaves were rst identi ed to species, and then each ant was carefully placed using tweezers into a sterilized 1.5 mL microcentrifuge tube (see details in Lin et al 15 ). Samples were vortexed in 600 μL sterilized water for a few seconds at 3,000 revolutions/min (rpm) using a vortex mixer (AL-VTX3000L, CAE technology Co., Ltd.), and were then soaked with 600 μL 70% ethanol to sterilize the ant's surface.…”

“…In the present study, we describe the bacterial community in O. unilateralis s. l.-infected ant cadavers and examine the biological properties of the predominant bacterial species. In Taiwan, O. unilateralis s. l. was found to infect eight sympatric species: seven Polyrhachis ant species and Camponotus punctatissimus 15 . Despite not being as highly host speci c as its relatives in Brazil, Japan, North America, and Thailand [16][17][18][19] , Taiwanese O. unilateralis s. l. prefer to infect P. moesta more than the other seven ant species.…”

“…Despite not being as highly host speci c as its relatives in Brazil, Japan, North America, and Thailand [16][17][18][19] , Taiwanese O. unilateralis s. l. prefer to infect P. moesta more than the other seven ant species. With P. moesta, Taiwanese O. unilateralis s. l displays better infection performance, including higher prevalence, developmental rate, and e ciency in host behavior manipulation 15 . Using a culture-dependent method to capture the bacterial community in the principal host, P. moesta, and an alternate sympatric host, P. wol , we found B. thuringiensis to be a predominant species in cadavers of both ant species.…”