SGER: Preliminary Assessment of Extinction of Crickets by Ants in Hawaii

9815919这项提案的目的是评估从非洲引入夏威夷的大头蚂蚁Pheidole Megacephala(大头蚂蚁)的影响，这种蚂蚁现在似乎直接威胁到蟋蟀和其他昆虫的多样性，并间接地威胁到该动物群的其他组成部分(蟋蟀是鸟类饮食的主要成分)。虽然引入的确切日期仍不确定，但有报道表明，这种蚂蚁在本世纪初就出现了，它对节肢动物的影响尤其严重。蚂蚁捕食的证据仍然是间接的，但它是强有力的。最近对蟋蟀流行情况的观察(1997年10月和1998年1月)表明，在以前富裕的地区，蟋蟀数量突然严重减少。这一悲观评估所依据的基线数据是在19年期间收集的。奥特研究了夏威夷所有岛屿上的蟋蟀的生物地理和系统学，在644个地理位置收集了数据，录制了11,000多首蟋蟀歌曲，并描述了大约190个新物种。在9年的时间里，肖研究了月桂属的系统发育、物种边界和行为，目的是了解这个岛屿实验室中新物种是如何产生的。在此期间，她参观了奥特(1994)所描述的许多板球丰富的地区。1997年10月，以前有大量蟋蟀的地区被发现实际上根本没有蟋蟀。对栖息地的检查发现了大量的大头蚂蚁。1998年1月再次进行了观察，当时没有听到蟋蟀的声音。奥特记录了考艾岛上207个地点的蟋蟀。这些遗址中的大多数包括劳帕拉属的成员。10月份和1月份的调查只包括一个长横断面。这项提案的目标是评估蚂蚁在一些低地和高原栖息地的影响。必须牢记厄尔尼诺现象的影响。由于1980年代早期的厄尔尼诺现象S对蟋蟀没有明显影响(尽管有相当大的干旱)，因此目前的种群数量下降可能与天气无关。还必须牢记引进植物的影响。在受影响的样带中，某些杂草植物的存在是显而易见的。但是，由于蟋蟀不是植物特有的寄主，它们生活在外来植物密度较高的地区，植被变化不太可能是种群崩溃的原因。必须考虑到自然捕食者-猎物循环正在发生的可能性。由于蚂蚁在夏威夷已经存在了90多年，目前的激增令人费解。这是典型的捕食者-猎物循环吗？这些地区过去曾被蚂蚁入侵过吗？会不会出现种群崩溃和随后的蟋蟀复兴？蚂蚁灭绝板球物种的可能性很高。塔希提岛的调查显示，莫雷亚现在没有山地板球动物--该地区过去曾有过地方性动物群。引入的蚂蚁数量如此之多，以至于设置板球陷阱是不可能的--诱饵在放置后几分钟内就会被蚂蚁移走。将确定目前月桂属六个物种的分布，并与过去研究的基线数据进行比较。种群水平将被评估，并与蚂蚁的存在或不存在相关联。哈佛大学和罗格斯大学将建立蟋蟀和蚂蚁群体，以评估蚂蚁在不同发育阶段对蟋蟀的影响。在野外种群的命运得到评估之前，板球群体也将被保存在几个实验室中。

0TTE 9815919 The goal of this proposal is to assess the effect of the ant, Pheidole megacephala (the big-headed ant) which has been introduced into Hawaii from Africa and now appears to threaten the diversity of crickets and other insects directly, and other components of the fauna indirectly (crickets are a major component of bird diet). Although the exact date of introduction remains uncertain; reports suggests the presence of this ant early in the century and its particularly devastating effect on arthropods. Evidence of ant predation is still indirect, but it is strong. Recent observations on the prevalence of crickets (October 1997 and January 1998) indicate a sudden and severe reduction of crickets in formerly rich areas. The baseline data upon which this pessimistic assessment is based was collected over a 19 year period. Otte studied the biogeography and systematics of crickets on all Hawaiian Island, collected at 644 geographic points, recorded more than 11,000 cricket songs, and described approximately 190 new species. Over a 9 year period Shaw has researched the phylogeny, species boundaries and behavior of the genus Laupola, with the goal of understanding how new species arise in this island laboratory. During that time she visited many of the cricket rich areas described by Otte (1994). In October 1997 areas previously having huge cricket populations were found to have virtually no crickets at all. Examination of the habitat revealed large numbers of big-headed ants. Observations were conducted again in January 1998 at which time no crickets were heard. Otte recorded crickets at 207 sites on the Island of Kauai. The majority of these sites included members of the genus Laupala. October and January surveys included only one long transect. The goal of this proposal is to assess the impact of ants at a number of lowland and highland habitats. The effect of El Nino must be kept in mind. Because an earlier El Nino in the 1980's had no visible effect on crickets (d espite considerable drought ) the current population decline may not be weather related. The effect of introduced plants must also be kept in mind. The presence of certain weedy plants in the affected transect is noticeable. but, because crickets are not host specific on plants and survive in areas with a high density of exotic plants, vegetational changes are not the likely cause of populations crashes. The possibility that a natural predator-prey cycle is occurring must be considered. Since the ants have been present in Hawaii for over 90 years, the current surge is baffling. Is this classical predator prey cycle? Have these areas been invaded by ants in the past? Will there be any populations crash and subsequent revival of crickets? The possibility that ants will exterminate cricket species is a high possibility. Surveys in Tahiti show that there is now no upland cricket fauna on Moorea-an area known to have had an endemic fauna in the past. Introduced ants are so abundant that the setting of cricket traps is impossible-baits are removed by ants within minutes of setting. The current distribution of six species of Laupala will be determined and compared to baseline data from past studies. Population levels will be assessed and correlated with presence or absence of ants. Crickets and ant colonies will be established at Harvard and Rutgers Universities to assess the effect of ants on crickets in various developmental stages. Cricket colonies will also be kept in several laboratories until the fate of field populations can be assessed.