生态学报  2016, Vol. 36 Issue (8): 2319-2326

文章信息

郑莉莉, 宋明华, 尹谭凤, 于飞海
ZHENG Lili, SONG Minghua, YIN Tanfeng, YU Feihai
青藏高原高寒草甸门源草原毛虫取食偏好及其与植物C、N含量的关系
Feeding preference of Gynaephora menyuanensis and its relationships with plant carbon and nitrogen contents in an alpine meadow on the Tibetan plateau
生态学报, 2016, 36(8): 2319-2326
Acta Ecologica Sinica, 2016, 36(8): 2319-2326
http://dx.doi.org/10.5846/stxb201410081973

文章历史

收稿日期: 2014-10-08
网络出版日期: 2015-08-18
青藏高原高寒草甸门源草原毛虫取食偏好及其与植物C、N含量的关系
郑莉莉1, 宋明华2, 尹谭凤2, 于飞海1     
1. 北京林业大学自然保护区学院, 北京 100083;
2. 中国科学院地理科学与资源研究所生态网络观测与模拟重点实验室, 北京 100101
摘要: 草食性昆虫对不同植物物种的取食存在偏好,这种取食偏好可能受其自身对蛋白质和碳水化合物的需求及二者平衡的调节。以青藏高原高寒矮嵩草草甸31种常见植物及门源草原毛虫为对象,通过饲喂实验,研究了草食性昆虫对不同物种和不同功能群植物的取食偏好,及其与植物叶片C、N含量和C:N之间的关系。在31种植物中,门源草原毛虫对19种植物进行了取食,尤其对矮嵩草、红棕薹草、藏异燕麦和垂穗披碱草四种植物表现出强烈的取食偏好,而对另外12种植物未进行任何取食。在物种水平上,门源草原毛虫取食量与植物叶片N含量呈显著负相关,与叶片C:N呈正相关。从功能群水平上看,门源草原毛虫对莎草类的取食偏好最大,而对豆科植物取食偏好最低;相应地,莎草类植物叶片N含量最低、C:N最高,而豆科植物叶片N含量最高、C:N最低。因此,即使在土壤有效氮匮乏、植物生长受氮素限制的高寒草甸生态系统,植物体内N含量的增加也可能不利于草食性昆虫的取食。门源草原毛虫对优势植物矮嵩草和垂穗披碱草的取食对高寒矮嵩草草甸物种共存和生物多样性维持可能具有重要的作用。
关键词: 草食性昆虫    适口性    植物功能群    取食行为    高山植物    幼虫    
Feeding preference of Gynaephora menyuanensis and its relationships with plant carbon and nitrogen contents in an alpine meadow on the Tibetan plateau
ZHENG Lili1, SONG Minghua2, YIN Tanfeng2, YU Feihai1     
1. School of Nature Conservation, Beijing Forestry University, Beijing 100083, China;
2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
Abstract: Phytophagous insects show feeding preference for different plant species, and such preference may be regulated by their demands for proteins and carbohydrates and the balance between them. Therefore, feeding preference of phytophagous insects may be closely related to carbon (C) content, nitrogen (N) content, and the C:N ratio of plants. Although many studies have investigated feeding preference of phytophagous insects for different plant species, relatively few have examined how plant functional groups affect feeding preference of phytophagous insects and whether their leaf C and N content, and C:N ratio matter. To examine feeding preference of phytophagous insects for different plant species and for different functional groups and its relationships with leaf C, N, and the C:N ratio of plants and functional groups, we conducted a feeding experiment in which we fed the larvae of a phytophagous insect, Gynaephora menyuanensis (Lymantriidae), with leaves of 31 common herbaceous plant species of four functional groups (sedges, grasses, legumes and forbs) collected in an alpine meadow dominated by Kobresia humilis on the Tibetan plateau. Fresh leaves of the 31 plant species were cut into pieces of the similar area (about 0.5 cm2) and fixed randomly on the arenas made of foam boards installed at the inner bottoms of six glass boxes (each measuring 1 m long × 1 m wide × 0.25 m high). Each box was treated as a block, containing ten leaf pieces of each of the 31 plant species collected on the same day. We put on the arena of each box 20 larvae of G. menyuanensis that were collected in the same meadow and had been starved for 24 hours, and measured consumption of each leaf piece (i.e., the percentage of leaf area loss) after 72 hours. Leaf area consumed by the larvae was further transformed into dry mass based on the relationship between leaf area and dry mass of each plant species. Of the 31 plant species, 19 were consumed by the larvae to different degrees, but the other 12 were not. The larvae showed strong feeding preference only for four species, i.e., K. humilis, Carex przewalskii, Helictotrichon tibeticum and Elymus nutans. At the species level, leaf consumption by the larvae was significantly negatively related with plant leaf N content and significantly positively related with the leaf C:N ratio. At the functional-group level, the sedges had the highest leaf consumption by the larvae, the lowest leaf N content and the highest leaf C:N ratio, whereas the legumes had the lowest leaf consumption, the highest leaf N, and the lowest leaf C:N ratio. We conclude that increasing N content of plants may not increase the feeding preference of phytophagous insects even in alpine meadow ecosystems where plant growth is highly limited due to the lack of soil available N. Our results also suggest that the strong feeding preference of G. menyuanensis larvae for the dominant species K. humilis and E. nutans may help in maintaining species coexistence and biodiversity in the alpine meadow dominated by K. humilis.
Key words: phytophagous insects    palatability    plant functional group    feeding behavior    alpine plants    larvae    

植物体内养分元素含量,尤其是碳(C)和氮(N)元素含量,是影响其适口性以及草食动物取食偏好的重要生物因素[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]。其部分原因在于,植物体内富含N的蛋白质和富含C的糖类是草食动物所需的两类基本物质,是其活动的能量来源,并影响其生长、发育和生殖[11]。很多研究表明,植物体内N含量增加或C:N降低会提高草食动物对植物的取食偏好[10, 11, 12, 13, 14]。然而,高的N含量并不是必然对应着高的草食动物取食偏好[9, 15, 16, 17]。例如,研究表明,食物中过高的植物N含量可导致亚洲草原一种蝗虫(Oedaleus asiaticus)生长的减缓[9]

对大多数草食性动物,尤其是草食昆虫,其食物都存在一个最佳N含量,当食物N含量大于或小于此最佳含量时均不利于其生长或发育[16, 18, 19, 20, 21]。因此,觅食那些蛋白质和碳水化合物含量或比例适合的食物是草食性动物所面临的主要挑战[21, 22, 23, 24]。对单食性和寡食性昆虫而言,其取食植物的种类有限,因而植物体蛋白质和碳水化物含量的较大变化会对草食性昆虫蛋白质/碳水化合物平衡造成显著影响[25]。而对于多食性昆虫来说,由于其取食的植物种类较多,而不同植物种类C、N含量存在很大的差异,因此昆虫对不同植物种的偏好对维持其自身蛋白质/碳水化合物的平衡具有重要意义。目前很多室内喂食实验主要围绕着草食昆虫对单个或少数几个植物物种的取食偏好展开的[19, 20, 21],而一些野外喂食实验虽包含多种植物,但多数仅就取食偏好进行了观测,没有把取食偏好与叶片养分元素含量进行关联[26, 27]。此外,草食昆虫是否对不同功能群植物存在取食偏好目前也并不清楚。

门源草原毛虫(G.menyuanensis Yan et Zhou)隶属鳞翅目(Lepidoptera)毒蛾科(Lymantriidae),是高寒草甸生态系统中常见的草食性昆虫[26, 27, 28],对牧草生长和群落初级生产力有十分显著的影响[26, 27]。青藏高原高寒草甸生态系统由于海拔高,年均温低,有机质分解慢,土壤缺乏速效N[29]。植物生长,尤其在春季受到低土壤有效N的限制[29],故植物体N含量相对较低。因此,青藏高原高寒草甸植物体内N含量很可能不足以超过门源草原毛虫的食物最佳N含量[16, 18, 19, 20, 21]。基于以上分析,提出如下假设:门源草原毛虫可能对高叶片N含量的植物物种和功能群有更高的取食偏好。

为验证这些假说,在青藏高原矮嵩草草甸选取了31种常见植物,在野外开展了门源草原毛虫饲喂实验,并对这31种植物的叶片C、N含量进行了测定。本文拟回答以下科学问题:(1)门源草原毛虫对矮嵩草草甸不同物种是否存在取食偏好?(2)如果存在,其取食偏好与植物叶片C含量、N含量和C:N是否存在相关性?(3)门源草原毛虫是否存在植物功能群水平上的取食偏好?(4)如果存在,植物功能群水平上的取食偏好是否与功能群水平的叶片C含量、N含量及C:N相关?

1 材料与方法 1.1 研究地概况

研究地位于海北高寒草甸生态系统定位研究站(简称“海北站”;37°37′ N,101°19′ E)。该站位于青藏高原东北隅的祁连山南坡谷地,海拔3200 m,属于典型高原大陆性气候,暖季短暂而凉爽,冷季寒冷而漫长。年平均气温-1.7 ℃,年极端最高气温27.6 ℃,极端最低气温-37.1 ℃。年降水量426—860 mm,80%集中于植物生长季的5—9月,蒸发量1160.3 mm。无绝对无霜期,年平均日照2462.7 h。由于其特殊的自然环境,多年生草本植物适应寒冷严酷的生境,形成了以矮嵩草(K.humilis)、金露梅(Potentilla fruticosa)及藏嵩草(K.tibetica)为主要建群种的植物群落类型。土壤是草毡寒冻雏形土,土壤发育年青、土层薄、有机质含量高。牧草生长低矮,群落结构简单,初级生产力低[30]

1.2 饲喂实验

2013年6月底,选取海北站附近矮嵩草草甸31种常见植物进行饲喂实验,所选植物种类及其功能群类型详见表 1。6月30日—7月5日,每天在植被均匀一致的草地上剪取上述31种植物的叶片,立即用自封袋装起来,带回室内用4 ℃的冰箱储存。对于每个植物种,从每天所取叶片样品中随机选取一部分用于C含量、N含量和比叶面积的测量,共计6个重复。

表 1 用于饲喂实验的31种植物种名、科名、功能群类型、门源草原毛虫取食量、叶片碳(C)含量、氮(N)含量和C:N Table 1 Species name, family name, functional type, leaf consumption by G. menyuanensis, leaf carbon (C) and nitrogen (N) contents and C:N of the 31 plant species used for the feeding experiment
种名
Species
科名
Family
功能群
Func.group
取食量/g
Consumption
叶片碳(C)
含量/%
Leaf carbon
(C) content
叶片氮(N)
含量/%
Leaf nitrogen
(N) content
叶片C:N
LeafC:N
矮嵩草Kobresia humilis莎草科Cyperaceae莎草sedge0.35±0.01a45.89±0.03d1.77±0.01o25.19±0.15a
异针茅Stipa aliena禾本科Gramineae禾草grass0.05±0.01def46.56±0.03c2.05±0.00n22.75±0.04b
垂穗披碱草Elymus nutans禾本科Gramineae禾草grass0.15±0.01bc45.18±0.02ef2.36±0.01k19.15±0.05g
早熟禾Poa annua禾本科Gramineae禾草grass0.08±0.01cde45.74±0.01d2.11±0.01mn21.68±0.13cd
藏异燕麦Helictotrichon tibeticum禾本科Gramineae禾草grass0.18±0.02b45.03±0.04ef1.79±0.01o25.21±0.15a
红棕薹草Carex przewalskii莎草科Cyperaceae莎草sedge0.19±0.01b45.07±0.04ef2.11±0.01mn21.35±0.08de
卷鞘鸢尾Iris potaninii鸢尾科Iridaceae杂类草forb0±0.00f45.84±0.01d2.76±0.01e16.59±0.04lm
铃铃香青Anaphalis hancockii菊科Compositae杂类草forb0±0.00f42.96±0.14k2.43±0.00jk17.66±0.04ijk
披针叶黄华Thermopsis lanceolata豆科Leguminosae豆科植物legume0±0.00f46.79±0.01c4.18±0.00a11.20±0.00qr
柔软紫菀Aster tataricus菊科Compositae杂类草forb0±0.00f44.48±0.04ghi2.44±0.00jk18.27±0.03hij
麻花艽Gentiana straminea龙胆科Gentianaceae杂类草forb0±0.00f47.52±0.05b3.02±0.01d15.72±0.02n
肉果草Lancea tibetica玄参科Scrophulariaceae杂类草forb0±0.00f47.47±0.03b2.05±0.00n23.12±0.03b
平车前Plantago depressa车前科Plantaginaceae杂类草forb0±0.00f40.68±0.01n2.58±0.00ghi15.76±0.02mn
疏齿银莲花Anemone obtusiloba毛茛科Ranunculaceae杂类草forb0±0.00f44.05±0.02ij2.64±0.01fgh16.70±0.03l
微孔草Microula sikkimensis紫草科Boraginaceae杂类草forb0.02±0.01ef41.57±0.03l3.81±0.02b10.92±0.05r
箭叶橐吾Ligularia sagitta菊科Compositae杂类草forb0±0.00f43.97±0.01ij3.06±0.01d14.38±0.03o
瑞苓草Saussurea nigrescens菊科Compositae杂类草forb0±0.00f45.14±0.02ef2.75±0.01e16.41±0.03lmn
高山唐松草Thalictrum alpinum毛茛科Ranunculaceae杂类草forb0±0.00f45.02±0.01ef2.56±0.01hi17.58±0.07jk
二裂委陵菜Potentilla bifurca蔷薇科Rosaceae杂类草forb0.06±0.01def45.79±0.02d2.10±0.00mn21.83±0.04cd
甘肃棘豆Oxytropis kansuensis豆科Leguminosae豆科植物legume0.02±0.00ef44.18±0.03hij3.63±0.00c12.17±0.01p
花苜蓿Medicago ruthenica豆科Leguminosae豆科植物legume0±0.00f45.15±0.01ef3.91±0.00b11.56±0.00pqr
高山豆Tibetia himalaica豆科Leguminosae豆科植物legume0±0.00f43.74±0.01j3.69±0.00c11.87±0.01pq
美丽风毛菊Saussurea pulchra菊科Compositae杂类草forb0±0.00f45.00±0.02efg2.22±0.00l20.27±0.03f
矮火绒草Leontopodium nanum菊科Compositae杂类草forb0±0.00f42.86±0.10k2.24±0.00l19.17±0.06g
蒲公英Taraxacum mongolicum菊科Compositae杂类草forb0±0.00f43.11±0.02k2.51±0.01ij17.15±0.03kl
线叶龙胆Gentiana farreri龙胆科Gentianaceae杂类草forb0±0.00f49.22±0.04a2.20±0.01lm22.39±0.08bc
圆萼刺参Morina chinensis川续断科Dipsacaceae杂类草forb0±0.00f43.80±0.06j2.38±0.01k18.43±0.11ghi
雪白委陵菜Potentilla nivea蔷薇科Rosaceae杂类草forb0±0.00f44.34±0.00hi2.68±0.00efg16.54±0.02lmn
美丽毛茛Ranunculus pulchellus毛茛科Ranunculaceae杂类草forb0±0.00f44.25±0.00hij2.35±0.01k18.80±0.06gh
鹅绒委陵菜Potentilla ansrina蔷薇科Rosaceae杂类草forb0.01±0.00f45.40±0.01de2.20±0.01lm20.64±0.04ef
珠芽蓼Polygonum viviparum蓼科Polygonaceae杂类草forb0.10±0.01cd44.67±0.02fgh2.72±0.01ef16.43±0.08lmn
所给数值为均值±标准误;不同字母表示均值存在显著差异

饲喂实验在六个透明有机玻璃盒里开展。每个盒子为长100 cm、宽100 cm、高25 cm的无盖长方体,其底面铺有泡沫板和滤纸,用于固定植物叶片片段和保持叶片片段的新鲜。为方便操作,在滤纸上用铅笔划出5 cm×5 cm的方格,每个植物片段固定在方格的一个角上。在每个盒子内,每种植物放置10个叶片片段,31种植物的310个叶片片段完全随机摆放。植物叶片片段用大头针固定,使其紧贴滤纸,滤纸定期喷水雾以保持湿润。每个叶片片段总面积大致相同,约0.5 cm2。宽叶植物剪成1 cm×0.5 cm的长方形,用大头针扎在其中心固定。对于禾本科等狭窄叶片,由于其宽度往往小于0.5 cm,按照其宽度剪成合适长度,最终保证总叶面积为0.5 cm2。例如,早熟禾叶片平均宽度为0.2 cm,将其叶片剪成2.5 cm长的片段固定,而针茅叶片平均宽度仅为0.05 cm,则将叶片剪成长度为5 cm的两段,将这两段叶片用大头针扎成十字形固定[31, 32]

由于剪取叶片片段和固定叶片片段的工作量很大,以及为了尽可能保证植物叶片的新鲜,在晚上将当天选取的植物叶片进行分段和固定,并保持滤纸湿润。在第2天9:00,即毛虫取食高峰到来之前,将取自野外样地并已饥饿24h的20只门源草原毛虫幼虫放入盒子的中央,开始实验。一天布置1个盒子,共计6个重复(盒子),每个盒子持续饲喂72h。实验结束后,估算每个叶片片段的被取食面积百分比。为了减小误差,所有估算均由同一个人完成。

1.3 植物性状测定

将采集的每种植物的若干新鲜叶片用扫描仪扫描后计算总叶面积,随后将这些叶片烘干称重,计算比叶面积(Specific leaf area,即单位重量叶面积)。植物叶片烘干后用球磨仪粉碎,然后采用元素分析仪测定每种植物每个样品中的C、N含量,每种植物测量6个样品。

1.4 数据分析

每个物种每个重复(盒子)中10个植物片段累计取食量(面积百分比)的平均值除以每个物种的平均比叶面积,得到每种植物每个重复的叶片取食量(leaf consumption,(g))。同时,将31种植物分为莎草、禾草、豆科植物和杂类草4个常用的功能类群[33, 34]

采用单因素方差分析(one-way ANOVA)检验门源草原毛虫叶片取食量、植物叶片C含量、N含量和C:N在物种之间和功能群之间的差异;多重比较采用Tukey法。通过回归分析,研究叶片取食量与叶片C含量、N含量及C:N之间的关系。所有分析采用SPSS version 17.0进行。

2 结果 2.1 门源草原毛虫对不同物种的取食偏好

门源草原毛虫对31种高寒草甸植物的取食偏好存在显著差异(F30,155=22.6,P <0.001;表 1)。矮嵩草的叶片取食量最高,显著高于藏异燕麦和红棕薹草;而藏异燕麦和红棕薹草与垂穗披碱草无显著差异,但显著高于珠芽蓼和早熟禾(表 1)。珠芽蓼和早熟禾与二裂委陵菜和异针茅无显著差异,但显著高于甘肃棘豆和微孔草(表 1)。二裂委陵菜和异针茅与甘肃棘豆和微孔草无显著差异,但显著高于其余的21种植物;甘肃棘豆和微孔草与其余的21种植物无显著差异(表 1)。

2.2 不同植物叶片N含量、C含量和C:N的差异

高寒草甸植物叶片中N含量、C含量及C:N均存在显著的种间差异(N含量: F31,160=878.7,P <0.001;C含量: F31,160=180.0,P <0.001;C: N:F31,160=703.5,P <0.001;表 1)。披针叶黄华的叶片N含量最高(4.18%),显著高于花苜蓿(3.91%)和微孔草(3.81%),以上3个物种叶片N含量显著高于高山豆(3.69%)和甘肃棘豆(3.63%,表 1),而藏异燕麦和矮嵩草的N含量最低,均为1.8%(表 1)。线叶龙胆叶片C含量最高,达49.2%,平车前最低,为40.7%(表 1)。矮嵩草叶片C:N最高(25.9),而微孔草的最低(10.9,表 1)。

2.3 门源草原毛虫取食与植物N含量、C含量及C:N的关系

门源草原毛虫叶片取食量与植物叶片N含量呈显著负相关关系(R2=0.16,P=0.017;图 1),与叶片C:N呈显著正相关关系(R2=0.26,P=0.001;图 1)。然而,门源草原毛虫取食量与植物叶片C含量没有显著的相关关系(R2=0.02,P=0.06;图 1)。

图 1 门源草原毛虫对31种植物叶片取食量与其叶片氮(N)含量、碳(C)含量以及C:N之间的相关关系 Fig.1 Relationships of leaf consumption by G. menyuanensis with leaf nitrogen (N) content, carbon (C) content and C:N of the 31 plant species
2.4 门源草原毛虫对不同功能群植物的取食偏好

门源草原毛虫对高寒草甸植物4种功能群的取食偏好存在显著差异(F3,185=97.6,P <0.001;图 2)。对莎草类的取食量显著高于禾草类(高1.3倍),对禾草类的取食量显著高于豆科(高16.9倍)和杂类草(高11.8倍),而对豆科植物和杂类草的取食量没有显著差异(图 2)。

图 2 门源草原毛虫对高寒草甸莎草、禾草、豆科植物和杂类草四类功能群植物的叶片取食量,以及四类功能群植物叶片N含量、C含量和C:N的均值和标准误 Fig.2 Leaf consumptions of the four plant functional groups (sedges, grasses, legumes and forbs) by G. menyuanensis, and leaf N and C contents and C:N of the four functional groups 不同字母表示均值在P=0.05水平上(Tukey 检验)存在显著差异
2.5 不同植物功能群叶片N含量、C含量及C:N的差异

高寒草甸植物4个功能群之间的N含量及C:N均存在显著差异(N含量: F3,185=101.9,P <0.001;C:N: F3,185=81.28,P <0.001)。豆科植物的叶片N含量为3.85%,显著高于杂类草,而杂类草显著高于莎草和禾草,但禾草和莎草间无显著差异(图 2)。莎草和禾草的的C:N分别为23.6和22.2,无显著差异,但均显著高于杂类草(图 2)。杂类草的C:N显著高于豆科植物(图 2)。4个功能群的叶片C含量无显著差异(图 2)。

3 讨论

门源草原毛虫取食了青藏高原矮嵩草草甸31种常见植物中的19种植物,表明门源草原毛虫的食性是广谱性的,属于多食性昆虫[26, 27]。尽管门源草原毛虫表现出多食性,但其仅对矮嵩草、红棕薹草、藏异燕麦和垂穗披碱草两种功能群的四种莎草或禾草植物种表现出很强的取食偏好(72小时内取食量超过0.1 g),其中对莎草类植物矮嵩草的取食量最大。然而,门源草原毛虫对豆科植物的取食量很少或基本不取食。因此,在功能群水平上门源草原毛虫对莎草类的取食偏好最大,禾草类其次,而对豆科类植物取食偏好最低。

一般认为,如果叶片中以N为基础的蛋白质和氨基酸含量低,那么植物N含量能较好地预测草食动物的取食偏好[12]。在这种情况下,植物叶片N含量和昆虫的成活率,生长发育将呈显著正相关关系[12, 13, 35, 36]。对青藏高原高寒草甸,植物生长受到土壤中低N的限制[37]。然而,我们发现,无论在物种水平还是功能群水平,门源草原毛虫取食量与青藏高原高寒草甸植物叶片N含量均呈现负相关关系。这些结果否定了我们的假设,表明即使在土壤有效氮匮乏、植物生长受N限制的高寒草甸生态系统,草食性昆虫也可能偏好取食叶片N含量低的植物。然而,要深入理解高寒植物叶片N含量与门源草原毛虫取食偏好之间的内在联系,还需进一步开展更加深入的生理和生化实验研究。

昆虫对植物种的不同取食偏好原因比较复杂,除了植物体内N含量和C:N之外,很多其他因素也起作用[1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 38]。一般而言,营养物质含量高(包括蛋白质、氨基酸、脂肪酸、碳水化合物、总能量、水、微量元素和维生素)、无毒、易被昆虫消化吸收的植物易被昆虫选择取食[39]。因此,一些物种的取食量随着N含量的增加而增加[4, 5, 6]。然而,碳水化合物是为草食动物快速提供能量、维持自身机能的重要物质。因此,草食动物一般来说都会有一个物种专一性的蛋白质/碳水化合物的带谱[19]。最优化的蛋白质与碳水化合物比例对于草食动物正常生长、发育和繁殖具有重要意义[19]。例如,蚂蚁自身喜好高碳水化合物的食物,但当它们被持续供应高蛋白质的食物时,就会遭受高的死亡率[40, 41, 42]。此外,植物的一些次级代谢产物也会影响草食昆虫的取食[43]。例如,C组成的次级代谢产物酚类、单宁等是适口性重要的控制因素[4],而单宁不容易消化[44, 45, 46],可作为抵御物质降低适口性[47]。经过长期的与自然环境和植物的协同进化,门源草原毛虫对食物的选择已经特化,这种特化的利用方式比普食性昆虫的利用效率更高[26, 48]。也有研究表明门源草原毛虫对其喜食的植物转化率最高[26]。另外,门源草原毛虫由于要抵御高寒草甸寒冷的自然条件,将较多资源分配给能提供能量的碳水化合物及非结构性蛋白质。究竟是哪种因素对门源草原毛虫食物选择起主导作用,尚待开展更加深入的生物化学方面的研究工作。

门源草原毛虫对不同植物物种取食偏好的差异可以影响高寒草地植物群落的结构和功能,并进一步影响整个生态系统的功能的发挥[27, 49]。从门源草原毛虫的食物谱和选食特征上看,其取食量较高的物种是矮嵩草和垂穗披碱草,而这些植物种是高寒矮嵩草草甸的优势物种,也是高寒草甸生态系统中的主要家畜牦牛和藏系绵羊(绵羊的藏系品种)喜食的优良牧草[27, 49]。这些草食性消费者对优势物种的大量取食,会显著地降低优势物种的优势度和地上生物量,当高密度草原毛虫发生时会引起矮嵩草草甸的严重退化[1]。而从另一方面看,毛虫的适当取食也对优势物种的扩张起到了抑制作用,使得多度较低的物种和稀有物种得以共存,从而维持了高寒矮嵩草草甸物种的共存和较高的多样性。因此,门源草原毛虫的取食偏好对青藏高原高寒矮嵩草草甸植物物种共存和生物多样性的维持可能有重要的意义。为此,需要进一步开展野外观测和实验,研究门源草原毛虫取食对高寒草甸群落结构(如物种组成和均匀度)和功能(如生产力)的影响。

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