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Dimensions of caterpillar fungus (Ophiocordyceps sinensis) decline—A response to Stewart et al.
Biological Conservation 167 (2013) 448–449
Contents lists available at ScienceDirect
Biological Conservation journal homepage: www.elsevier.com/locate/biocon
Letter to the Editor Dimensions of caterpillar fungus (Ophiocordyceps sinensis) decline—A response to Stewart et al.
Stewart and Bushley (2013), citing our study (Shrestha and Bawa, 2013), state that ‘we disagree that the data presented in Shrestha and Bawa’s recent study unequivocally demonstrates that there is an overall decline in caterpillar fungus abundances’. They conclude that ‘overall levels of caterpillar fungus may indeed be declining’ and that ‘our field research in Yunnan from 2007– 2011 has similarly found that harvesters have experienced a per capita decline during the past decade.’ We are therefore not certain if Stewart and Bushley, 2013 agree or disagree with the results of our study. Nevertheless, we would like to address their concerns. Stewart and Bushley (2013) criticize our statement that increasing trade is responsible for declining populations. However, apart from trade induced over-harvesting, we have discussed four other possible causes of decline: (a) decrease in moth and larval populations due to loss or degradation of host plant resources for moths and larvae; (b) modification of the soil microhabitats congenial to fungal spores by the harvesters; (c) increased grazing intensity in high-altitude pastures as local harvesters take their cattle with them; and (d) climate changes (Shrestha and Bawa, 2013). Unfortunately, they overlooked the discussion part of our paper and misinterpreted the conclusion. We reiterate that over-harvesting or human encroachment is the most visible disturbance to the caterpillar fungus habitat. Although the production in China is hundreds of times more than in Nepal, based on our calculation, per unit human pressure on the caterpillar fungus habitat is much higher in Nepal than in China. Therefore, the scale of harvesting comparatively is much larger in Nepal. Second, Stewart and Bushley (2013) question one of our citations of popular media report, which is based on interviews of several people and experts on the field. We found that report from Nepal is reliable and in line with our results. We have also cited evidence from other studies conducted in Tibet, Bhutan and India. But even in China, overall production has reportedly declined (Zhang et al., 2012). We recently compiled total traded amount of caterpillar fungus in Bhutan based on the auction data and found a similar decline. More importantly, Stewart and Bushley (2013) also found similar decline in per capita harvest in Yunnan, China. Had they provided quantitative data about per capita decline, as we did, we could assess the difference between our results. Third, Stewart and Bushley’s view that there has been an increase in number of traders with the increase in the market price and demand may be correct in other regions. However, in our study area in Dolpa, the number of middlemen (workers for district level traders) has increased but the number of district level traders has remained the same. Based on our observations and discussions with middlemen and traders, the trade of caterpillar
0006-3207/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocon.2013.07.026
fungus is syndicated by a handful of traders. Therefore, increase in number of middlemen has not changed the overall trade volume or the traders. Fourth, Stewart and Bushley (2013) raise concern about our figures of total trade volume based on the revenue data stating ‘how the formal figures are contingent upon whether traders use official channels and sell their volumes in Kathmandu or other government centers.’ We have discussed the margin of error in the revenue data—the sole authentic source of information available to estimate total trade volume. Since 2001, the price of caterpillar fungus has increased up to 2300% in Nepal, but the per unit revenue rate (Nepalese Rupees 20,000 per kg) has not increased. In fact, revenue collected per kilogram was further reduced to half (Nepalese Rupees 10,000 per kg) in 2006. Hence the revenue rate, expressed as percentage of market price was significantly decreased from 20% in 2001 to 1% in 2011 even though the price collected by traders has sharply increased. Thus, traders are more willing to use formal channels to pay revenue to avoid risk of getting their goods confiscated by law enforcement agencies. Therefore, we believe that recent revenue data of caterpillar fungus has been more reliable than in the past. We agree that the ecology and natural history of the caterpillar fungus is largely unknown and have pointed this out in our manuscript. Furthermore, there are several controversial claims about the life cycle, time required to complete the life cycle, and mode of infection in this species. Zhang et al. (2012) reviewed the life cycle of caterpillar fungus and showed uncertainty about how the caterpillar is infected by the fungus. The infection might be due to the ingestion of a fungal spore, the penetration of fungal hyphae to the insect spiracle, or the direct penetration of germinated ascospore (conidium) adhering to the insect surface (Zhang et al., 2012). Our statement that ‘current harvesting impedes the timely release of spore on soil inhibiting reproduction’ is based on assumption that the spore (ascospore in case of caterpillar fungus) release from mature specimens is preceded by harvest from the collectors. Sexual spores are the principal sources of propagation of the caterpillar fungus from one generation to another (from one year to the next) and are produced by stromata of mature specimens only (usually from late July to August) (personal communication with Dr. Bhushan Shrestha). Early harvesting does not permit sexual spore release, which reduces the likelihood of infection of the new caterpillar. Asexual spores, on the other hand, produced by germinating hyphae on the surface of the caterpillar function as infecting propagule or as a means to resist adverse conditions in the soil. Overall, arguments of Stewart and Bushley (2013) do not convince us to revise our conclusions. In fact our field work in 2012, not reported in our paper based on field work in 2011, indicated further decline in harvest of the fungus.
Letter to the Editor / Biological Conservation 167 (2013) 448–449
References Shrestha, U.B., Bawa, K.S., 2013. Trade, harvest, and conservation of caterpillar fungus (Ophiocordyceps sinensis) in the Himalayas. Biol. Conserv. 159, 514–520. Stewart, M.O., Bushley, K.E., Yongping, Y., 2013. Towards deeper engagement with the social–ecological dimensions of caterpillar fungus (Ophiocordyceps sinensis) production and governance in the Himalayas. Biol. Conserv.. Zhang, Y., Li, E., Wang, C., Li, Y., Liu, X., 2012. Ophiocordyceps sinensis, the flagship 507 fungus of China: terminology, life strategy and ecology. Mycology 3, 2–10.
⇑
Uttam Babu Shrestha Department of Biology, University of Massachusetts, Boston, MA 02125, USA ⇑ Corresponding author. Tel.: +1 8574138812. E-mail address: [email protected]
449
Kamaljit S. Bawa Department of Biology, University of Massachusetts, Boston, MA 02125, USA Ashoka Trust for Research in Ecology and The Environment (ATREE), Bangalore, India
Contents lists available at ScienceDirect
Biological Conservation journal homepage: www.elsevier.com/locate/biocon
Letter to the Editor Dimensions of caterpillar fungus (Ophiocordyceps sinensis) decline—A response to Stewart et al.
Stewart and Bushley (2013), citing our study (Shrestha and Bawa, 2013), state that ‘we disagree that the data presented in Shrestha and Bawa’s recent study unequivocally demonstrates that there is an overall decline in caterpillar fungus abundances’. They conclude that ‘overall levels of caterpillar fungus may indeed be declining’ and that ‘our field research in Yunnan from 2007– 2011 has similarly found that harvesters have experienced a per capita decline during the past decade.’ We are therefore not certain if Stewart and Bushley, 2013 agree or disagree with the results of our study. Nevertheless, we would like to address their concerns. Stewart and Bushley (2013) criticize our statement that increasing trade is responsible for declining populations. However, apart from trade induced over-harvesting, we have discussed four other possible causes of decline: (a) decrease in moth and larval populations due to loss or degradation of host plant resources for moths and larvae; (b) modification of the soil microhabitats congenial to fungal spores by the harvesters; (c) increased grazing intensity in high-altitude pastures as local harvesters take their cattle with them; and (d) climate changes (Shrestha and Bawa, 2013). Unfortunately, they overlooked the discussion part of our paper and misinterpreted the conclusion. We reiterate that over-harvesting or human encroachment is the most visible disturbance to the caterpillar fungus habitat. Although the production in China is hundreds of times more than in Nepal, based on our calculation, per unit human pressure on the caterpillar fungus habitat is much higher in Nepal than in China. Therefore, the scale of harvesting comparatively is much larger in Nepal. Second, Stewart and Bushley (2013) question one of our citations of popular media report, which is based on interviews of several people and experts on the field. We found that report from Nepal is reliable and in line with our results. We have also cited evidence from other studies conducted in Tibet, Bhutan and India. But even in China, overall production has reportedly declined (Zhang et al., 2012). We recently compiled total traded amount of caterpillar fungus in Bhutan based on the auction data and found a similar decline. More importantly, Stewart and Bushley (2013) also found similar decline in per capita harvest in Yunnan, China. Had they provided quantitative data about per capita decline, as we did, we could assess the difference between our results. Third, Stewart and Bushley’s view that there has been an increase in number of traders with the increase in the market price and demand may be correct in other regions. However, in our study area in Dolpa, the number of middlemen (workers for district level traders) has increased but the number of district level traders has remained the same. Based on our observations and discussions with middlemen and traders, the trade of caterpillar
0006-3207/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocon.2013.07.026
fungus is syndicated by a handful of traders. Therefore, increase in number of middlemen has not changed the overall trade volume or the traders. Fourth, Stewart and Bushley (2013) raise concern about our figures of total trade volume based on the revenue data stating ‘how the formal figures are contingent upon whether traders use official channels and sell their volumes in Kathmandu or other government centers.’ We have discussed the margin of error in the revenue data—the sole authentic source of information available to estimate total trade volume. Since 2001, the price of caterpillar fungus has increased up to 2300% in Nepal, but the per unit revenue rate (Nepalese Rupees 20,000 per kg) has not increased. In fact, revenue collected per kilogram was further reduced to half (Nepalese Rupees 10,000 per kg) in 2006. Hence the revenue rate, expressed as percentage of market price was significantly decreased from 20% in 2001 to 1% in 2011 even though the price collected by traders has sharply increased. Thus, traders are more willing to use formal channels to pay revenue to avoid risk of getting their goods confiscated by law enforcement agencies. Therefore, we believe that recent revenue data of caterpillar fungus has been more reliable than in the past. We agree that the ecology and natural history of the caterpillar fungus is largely unknown and have pointed this out in our manuscript. Furthermore, there are several controversial claims about the life cycle, time required to complete the life cycle, and mode of infection in this species. Zhang et al. (2012) reviewed the life cycle of caterpillar fungus and showed uncertainty about how the caterpillar is infected by the fungus. The infection might be due to the ingestion of a fungal spore, the penetration of fungal hyphae to the insect spiracle, or the direct penetration of germinated ascospore (conidium) adhering to the insect surface (Zhang et al., 2012). Our statement that ‘current harvesting impedes the timely release of spore on soil inhibiting reproduction’ is based on assumption that the spore (ascospore in case of caterpillar fungus) release from mature specimens is preceded by harvest from the collectors. Sexual spores are the principal sources of propagation of the caterpillar fungus from one generation to another (from one year to the next) and are produced by stromata of mature specimens only (usually from late July to August) (personal communication with Dr. Bhushan Shrestha). Early harvesting does not permit sexual spore release, which reduces the likelihood of infection of the new caterpillar. Asexual spores, on the other hand, produced by germinating hyphae on the surface of the caterpillar function as infecting propagule or as a means to resist adverse conditions in the soil. Overall, arguments of Stewart and Bushley (2013) do not convince us to revise our conclusions. In fact our field work in 2012, not reported in our paper based on field work in 2011, indicated further decline in harvest of the fungus.
Letter to the Editor / Biological Conservation 167 (2013) 448–449
References Shrestha, U.B., Bawa, K.S., 2013. Trade, harvest, and conservation of caterpillar fungus (Ophiocordyceps sinensis) in the Himalayas. Biol. Conserv. 159, 514–520. Stewart, M.O., Bushley, K.E., Yongping, Y., 2013. Towards deeper engagement with the social–ecological dimensions of caterpillar fungus (Ophiocordyceps sinensis) production and governance in the Himalayas. Biol. Conserv.. Zhang, Y., Li, E., Wang, C., Li, Y., Liu, X., 2012. Ophiocordyceps sinensis, the flagship 507 fungus of China: terminology, life strategy and ecology. Mycology 3, 2–10.
⇑
Uttam Babu Shrestha Department of Biology, University of Massachusetts, Boston, MA 02125, USA ⇑ Corresponding author. Tel.: +1 8574138812. E-mail address: [email protected]
449
Kamaljit S. Bawa Department of Biology, University of Massachusetts, Boston, MA 02125, USA Ashoka Trust for Research in Ecology and The Environment (ATREE), Bangalore, India