Colonization and Recovery of Invertebrate Ecosystem Engineers during Prairie Restoration

Ants (Hymenoptera: Formicidae) and earthworms (Oligochaeta) are considered ecosystem engineers because they form biogenic structures in the soil that influence resource supply. The objectives of this study were to quantify recovery dynamics of these invertebrate groups across a chronosequence of restored prairies and elucidate whether changes in the abundance and biomass of ants and earthworms were related to key plant and ecosystem properties. We sampled ants and earthworms from cultivated fields, grasslands restored from 1 to 21 years, and native prairie. Ant abundance and biomass peaked between 5 and 8 years of restoration and abundance was 198 times greater than cultivated fields. Earthworm abundance increased linearly across the chronosequence and became representative of native prairie, but all earthworm populations were dominated by European species. Ant abundance and biomass were positively correlated with plant diversity and plant richness, whereas earthworm abundance biomass was only related to surface litter. These results demonstrate that earthworm abundance increases with time since cessation of cultivation and concomitant with prairie establishment, whereas the abundance and biomass of ants are more related to the structure of restored plant communities than time. The dominance of exotic earthworms in these restorations, coupled with their capacity to alter soil properties and processes may represent novel conditions for grassland development.     

A review of myrmecophilous mites of the family Microdispidae (Acari,Heterostigmatina) of Western Siberia

Five species of myrmecophilous microdispid mites (Acari: Microdispidae) are recorded from Western Siberia, Russia. Unguidispus lasii Kurosa, 1979, Unguidispus japonicus Kurosa, 1979, Caesarodispus minutus (Sevastianov, 1981), and Caesarodispus samsinaki (Mahunka, 1967), comb. n. are reported from Russia for the first time. Unguidispus polyctenus (Sevastianov, 1969) and Caesarodispus samsinaki are redescribed. The keys to species of the genera Unguidispus Mahunka, 1970 and Caesarodispus Mahunka, 1977 are provided.     

Body size effects on locomotion and load carriage in the highly polymorphic leaf-cutting ants Atta colombica and Atta cephalotes

Leaf-cutting ants reduce their walking speed under the weightof the leaf fragments they carry, an effect likely to havesome consequence for the foraging performance of a colony.I manipulated loads carried by workers from two Atta speciesto determine how load mass and body size affect walking speed.A comparison of speeds before and after load manipulation indicatesthat change in load mass has a linear effect on velocity. Several different regression models of speed as a function of loadsand body size have similar fit to the data, so a single bestmodel cannot easily be identified. However, there is statisticalevidence that the slope of the linear effect is more pronouncedfor smaller ants, an outcome most consistent with a regression model based on loading ratio, a metric that scales load massrelative to body mass. I then examined the effect of loadingratio on the leaf transport rate (the product of load massand carriage velocity). It has been claimed that this rateis maximized over a range of loading ratios that is the samefor all ants regardless of their size. However, I found thata latent body mass effect persists in the relation of transportrate to loading ratio, even though loading ratio is alreadyscaled relative to body mass. The maxima seem to be reachedonly at artificially elevated loading ratios, so that transportrates with natural fragments tend to be sub-maximal. This conclusionis in agreement with analytical predictions of rate-maximizingload masses derived from the regression models. Thus, loadingratio does not adequately scale load mass relative to bodysize when used in this context (effect on leaf transport rate),and should be used cautiously. Ants are likely to accommodateloads through modulation of both stride length and step frequency,but precisely how this takes place requires future study.     

Foraging Area Marking in Two Related Tetramorium Ant Species (Hymenoptera: Formicidae)

The related ants Tetramorium caespitum and T. impurum mark their foraging area in a species-specific, home range and short-lasting manner. Indeed, ants reaching a new area have a slow linear speed which increases during the marking. Conspecific ants are arrested and attracted by marked areas, while heterospecific ants are reluctant to visit them. However, when the latter do visit marked areas, they move more quickly and less sinuously than conspecific ants and do not stay on the areas. The marking is performed in about 3 min by T. caespitum and in 3 to 6 min by T. impurum. If not reinforced, the marking vanishes in the same time intervals. Neither poison gland nor last sternite extracts reproduce the activity of naturally marked areas, whereas a Dufour gland extract does exactly that. Foraging ants touch the ground with the tip of their gaster. Consequently, we can postulate that the workers mark their foraging area with the contents of this gland, which is associated with the sting apparatus, and that they deposit with the extremity of the gaster. Alien conspecific ants are seldom aggressive to one another, even on marked areas. When encountering each other on unmarked areas, heterospecific ants present some aggressive reactions. On marked areas, their aggressiveness is enhanced and intruder ants are restless, while resident ones walk freely. On ground marked by T. impurum, ants of this species are more aggressive than antagonistic T. caespitum workers. The marking of foraging areas thus induces defense against heterospecifics but not against conspecific ants.     

红火蚁入侵草坪过程中蚂蚁类群变动趋势

观察研究了红火蚁入侵草坪之后蚂蚁群落结构的变动趋势。对各处理区在不同时期的蚂蚁优势种进行了分析,结果表明,与对照区相比红火蚁入侵后各处理区的蚂蚁优势种发生了明显改变,红火蚁替代了原来的优势蚂蚁种类,并在数量上占主导地位,而且各处理区的蚂蚁类群多样性、均匀度降低,优势度明显增大。通过分析红火蚁入侵过程中各处理区的蚂蚁类群相似性,表明轻度发生区与对照区的蚂蚁类群相似性系数q一直处在0.25-0.50之间,为中等不相似;中度发生区与对照区的蚂蚁类群相似性系数q一直处在0.075-0.444之间,为中等不相似或极不相似;重度发生区与对照区的蚂蚁类群相似性系数q一直处在0.0-0.222之间,为极不相似,这也说明了不同的红火蚁危害程度对本地蚂蚁类群结构的影响是不同的,红火蚁种群数量越大,对本地蚂蚁类群的影响也越大,排挤或取代它们所需要的时间也越短。     

舞草种子的蚂蚁传播

舞草(Codariocalyx motorius)由于其小叶具有自身"摆动"的功能,从而具有较高的观赏价值.在长期的演化过程中,舞草与蚂蚁形成了互惠共生的关系舞草种子生成了附生其上的能吸引蚂蚁的油质体,蚂蚁在搬运取食中,使舞草种子得以传播.舞草种子最重要的传播者是圆叶铺道蚁(Tetramorium cyclolobium Xu et Zheng)和布立毛蚁(Paratrechina bourbonica Forel).另外长足光结蚁(Anoplolepis gracilipes Smith)和两种大头蚁(Pheidole sp.1和sp.2)也搬运其种子.野外试验表明,圆叶铺道蚁日搬运活动与气温呈显著正相关,即y(搬运种子数)=-9.5038+0%5608X(气温)(r=0.7196**,n=33,P＜0.01),中午搬运效率达到高峰.布立毛蚁日搬运活动在上、下午各有一个高峰,上午的高峰出现时间不稳定,下午的高峰出现在1 600～1800.舞草种子上附生的油质体是吸引蚂蚁并产生搬运行为的主要物质.化学分析表明,油质体富含蚂蚁生长发育所必需的10种氨基酸和多种无机元素.样地采用陷阱诱捕蚂蚁的调查显示,5种搬运者中,圆叶铺道蚁数量最大,分别占蚂蚁总量的8.26%和搬运蚂蚁总量的48%.这说明圆叶铺道蚁在舞草种子的搬运中起着主要作用.     

西双版纳傣族“龙山”片断热带雨林蚂蚁类群结构与多样性研究

在西双版纳热带雨林地区,采用陷阱法（Pitfall traps) 对2类龙山片断雨林和保护区连续雨林蚂蚁类群进行取样调查,样地内共获取蚂蚁9196号,隶属6亚科,28属,53种,其属种和个数数量以切叶蚁亚科（Myrmicinae)最多。不同生境群落组成分差异较大,优势种变化明显。对3种蚂蚁类群多样性研究分析表明：保护区连续雨林的多样性、均匀性指数高于龙山片断林,群落相似性以2类龙山林最高,各林地蚂蚁类群物种分布的种－多度关系为对数级数模式。片断化雨林面积、植被结构、隔离程度及状况和人为干扰程度是影响蚂蚁类群结构和多样性的重要因素。     

蚂蚁对不同土地利用的物种响应及生物指示——以云南为例

为了揭示不同土地利用状态下蚂蚁群落在物种层面的变化,采用陷阱法调查了云南省绿春县天然次生林、桉树林、紫胶林、紫胶-玉米混农林、橡胶林、旱地和农田7种类型样地地表蚂蚁群落。共采集地表蚂蚁16704头,隶属于8亚科44属106种。不同类型样地地表蚂蚁群落结构有差异(ANOSIM Global R=0.786,P=0.01),桉树林、紫胶林和紫胶玉米混农林地表蚂蚁群落结构与天然次生林相似,与橡胶林和农田不相似。不同样地具有各自的特有种,旱地和农田中各为1种,其余样地有5-8种。在多个样地中均有出现的物种在不同类型样地中的多度变化明显。对群落结构相似性贡献率≥5%的特征物种分析显示,天然次生林中的特征物种明显与旱地和农田不同。天然次生林中的指示物种为毛发铺道蚁Tetramorium ciliatum,桉树林中为亮褐举腹蚁Crematogaster contemta,紫胶林中为飘细长蚁Tetraponera allaborans,旱地中为伊大头蚁Pheidole yeensis。不同特征物种及指示物种的生物学特性与不同样地特征相关联。地表蚂蚁通过物种组成及多度变化响应土地利用变化,蚂蚁特征物种可以作为指示物种的补充。