Case studies on the function and evolution of insect coloration

Changku Kang 한국응용곤충학회 2022 한국응용곤충학회 학술대회논문집 Vol.2022 No.10

Body size affects the evolution of hidden colour signals in moths

Kang, Changku,Zahiri, Reza,Sherratt, Thomas N. Royal Society 2017 Proceedings, Biological sciences Vol.284 No.1861

<P>Many cryptic prey have also evolved hidden contrasting colour signals which are displayed to would-be predators. Given that these hidden contrasting signals may confer additional survival benefits to the prey by startling/intimidating predators, it is unclear why they have evolved in some species, but not in others. Here, we have conducted a comparative phylogenetic analysis of the evolution of colour traits in the family Erebidae (Lepidoptera), and found that the hidden contrasting colour signals are more likely to be found in larger species. To understand why this relationship occurs, we present a general mathematical model, demonstrating that selection for a secondary defence such as deimatic display will be stronger in large species when (i) the primary defence (crypsis) is likely to fail as its body size increases and/or (ii) the secondary defence is more effective in large prey. To test the model assumptions, we conducted behavioural experiments using a robotic moth which revealed that survivorship advantages were higher against wild birds when the moth has contrasting hindwings and large size. Collectively, our results suggest that the evolutionary association between large size and hidden contrasting signals has been driven by a combination of the need for a back-up defence and its efficacy.</P>

Camouflage Through Behavior in Moths: The Role of Background Matching and Disruptive Coloration

Changku Kang,Martin Stevens,Jongyeol Moon,Sangim Lee,Piotr G. Jablonski 한국응용곤충학회 2014 한국응용곤충학회 학술대회논문집 Vol.2014 No.04

Camouflage can be attained via mechanisms such as background matching (resembling the general background) and disruptive coloration (hindering the detection of an animal’s outline). However, despite much conceptual work with artificial stimuli there have to date been few studies of how such camouflage types work in real animals in their natural environments. Here, using avian vision models and image analysis, we tested which concealing mechanisms operate to provide camouflage during behavioral choice of a resting position in two bark-resting moths, Hypomecis roboraria and Jankowskia fuscaria. We found that both species reinforced their crypticity in terms of both background matching and disruptive coloration. However the detailed mechanisms (such as achromatic/chromatic matching or pattern direction matching) that each species exploits differed between the two species. Additionally, we found substantial correlation between the degree of background matching and disruptive coloration, which supports previous work suggesting that these two different concealing mechanisms work together to confer camouflage. Our results clearly demonstrate that an appropriate behavioral choice of background is essential to improve camouflaged against natural predators, and highlight the interrelation between different concealing mechanisms in real prey.

The incidence of abnormalities in the fire-bellied toad, Bombina orientalis, in relation to nearby human activity

Kang, Changku,Shin, Yujin,Kim, Ye Eun,Moon, Jongyeol,Kang, Jae Yeon,Jang, Yikweon The Ecological Society of Korea 2016 Journal of Ecology and Environment Vol.39 No.1

Declines in amphibian populations are occurring worldwide, and have been attributed to many factors, including anthropogenic environmental changes. One of the ramifications of such declines is abnormalities in many amphibian species. A strong association has been detected between human activities and abnormalities in amphibian populations, but studies on this association are largely focused on lentic species. In this study, it was analyzed whether the degree of local human activity was associated with the rate of abnormalities in Bombina orientalis which inhabited lotic environments. We found that the proportions of abnormalities in wild populations of B. orientalis increased, when i) the closest human land use was located within 100 m from the frogs' habitat, and ii) the proportion of human land use within a 300-m radius was high. Our findings suggest that human activity has a negative impact on the fitness of nearby amphibian populations, and that wild populations very close to human-induced disturbance are affected.

How do animals “see” the colors of insect? Visual modelling of animal vision to study insect coloration

Changku Kang,Jongyeol Moon,Piotr G. Jablonski 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.10

The diverse color pattern of insects are products of natural/sexual selection and affect their survival and reproductive success. Therefore understanding the function of the color patterns is critical to understand their life-history traits such as defensive/territorial behavior or mating strategies. However how we (humans) see and perceive their colors does not reflect the true nature of the insect colors because the insect colors have evolved to work best for the appropriate receiver. For example, defensive coloration have evolved to deceive predators’ eyes, and sexual traits of males have evolved to attract the eyes of the conspecific females. The visual system (therefore the perception of color, too) substantially differ between species and it is important to consider the appropriate receiver’s point of view (visual system) to properly understand the functional aspect of insect color pattern. Here I introduce the concepts of visual modelling of animals’ point of view to study insect coloration and present a case study research on camouflage of moths.

Body size affects the evolution of hidden color signals in insects

Changku Kang,Karl Loeffler-Henry,Thomas N. Sherratt 한국농약과학회 2018 한국농약과학회 학술발표대회 논문집 Vol.2018 No.10

Body size affects the evolution of hidden color signals in insects

Changku Kang,Karl Loeffler-Henry,Thomas N. Sherratt 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.10

Deimatic display 는 평상시에는 위장으로 자신을 보호하는 동물들이 포식자에게 위협당하였을 때에만 일시적으로 화려한 경고색을 보여줌으로써 포식자를 놀라게 하여 자신을 보호하는 방어전략이다. 본 연구에서는 3가지의 서로 다른 연구 방법을 이용하여 이 방어전략의 진화에 대해 연구하였으며, 연구의 모델로는 태극나방과 (Erebidae)의 나방을 이용하였다. 첫 번째로 deimatic display 전략이 어떤 종에서 진화하였으며, 이 전략이 동물의 몸 크기와 함께 진화하였는지를 계통수 분석을 이용한 방법으로 연구하였다. 연구 결과 deimatic display 는 몸 크기가 상대적으로 큰 곤충에서 선택적으로 진화하였다는 사실을 발견하였다. 두 번째로 deimatic display 전략이 왜 body size 가 큰 종에서 진화하였는지를 이론적으로 검증하기 위하여 수학적 모델링을 활용, deimatic display 와 몸 크기와의 이론적인 관계를 연구하였다. 이론적 모델링이 시사하는 바는 1) 몸 크기가 클수록 위장이 실패할 확률이 높으며, 2) 몸 크기가 클수록 deimatic display 가 포식자를 위협하는 효과가 클수록 이러한 진화적인 관계가 생성될 수 있다는 점을 발견하였다. 마지막으로 수학적 모델링에서 도출된 결과를 실험적으로 검증하기 위하여 로보틱스 기술을 활용, deimatic display 행동을 보이는 인공나방로봇을 제작하였다. 제작된 인공나방 로봇의 날개크기와 날개색채를 변화시켜가며 나방의 크기가 커질수록 deimatic display 전략이 포식자(조류)를 위협하는데 더 효과적인지를 테스트하였으며, 실험 결과 deimatic display 전략은 나방의 사이즈가 클수록 더 효과적이라는 사실을 입증하였다. 추가 연구 결과 이러한 큰 크기 – 숨겨진 화려한 색채의 관계는 태극나방과 뿐만이 아니라 메뚜기목, 대벌레목, 사마귀목, 그리고 누에나방과(나비목)에서도 발견됨을 확인하였다. 본 연구의 결과는 deimatic display 전략이 큰 크기와 공진화하였음을 보여주며, 이러한 크기-색채 공진화는 deimatic display 전략의 효용성과 밀접한 관련을 가지며 이루어졌다는 사실을 보여준다.

Co-evolutionary patterns between false heads and associated traits in lycaenid butterflies

San Kang,Do Hoon Cha,Changku Kang 한국응용곤충학회 2024 한국응용곤충학회 학술대회논문집 Vol.2024 No.04

Hindwings of many lycaenid butterflies have a unique tail-like wing structure referred to as a false head, which actually mimics the antennae. False heads increase butterfly survival by directing predatory attacks towards the false heads thereby enhancing the chance of escape. In this study, using discrete character evolution models of European and American butterflies, we examined the co-evolutionary patterns between false head structures and two associated traits: a highly contrasting color patch neighboring the false head, and hindwing rubbing behaviors. The former is considered a eye-mimicking structure that enhances the effectiveness of false head, and latter generates the movement of false heads which likely increases the success of false head deception. Our findings demonstrate that false heads are ancestral states for both European and American lycaenids. Both contrasting colors and hindwing rubbing behaviors follow correlated evolution models, suggesting that these traits co-evolved in lycanid butterflies. However, specific evolutionray patterns differed between the two continents.

Which sensory organ is used to find more cryptic positions and body orientations in moths?

Jongyeol Moon,Changku Kang,Piotr G. Jablonski 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.10

Geometrid moths are well known for their camouflage. Their wing color patterns resemble tree bark which is their preferential resting place. After landing on tree bark, many of them show the re-positioning behavior which makes the moths more cryptic effectively. Previous study revealed that moths perceive structural cues from tree bark to position their bodies. However, to date, it is not clear which sensory organ is used during re-positioning behavior. We performed a series of experiments to find out how (i.e. by using which sensory organs) moths seek out an appropriate position and body orientation. We used a geometrid moth, Jankowskia fuscaria, to test our hypothesis. We hypothesized that one of four sensory organs (eyes, antennae, front legs, and wings) may be responsible for their ability to find more cryptic position and body orientation. We amputated one of these organs and observed whether they are still able to find a cryptic position. The results indicates that visual cue is essential for their cryptic-positioning searching behavior, but antennae or front legs are not. Tactile cues from their wings seem to have a role in their behavior, but the evidence is flimsy. Therefore we cautiously conclude that moths mainly rely on visual cues (most likely through eyes) to orient their bodies on resting place, but additional tactile cues from their wings seem to play an additional role.

A sheep in wolf’s clothing: A microlepidopteran species mimics jumping spiders

Wonbin Lim,Changku Kang 한국응용곤충학회 2024 한국응용곤충학회 학술대회논문집 Vol.2024 No.04

깡충거미과의 모습을 의태하여 시각적 포식자인 깡충거미로부터 자신을 보호하는 전략은 여러 나비목 곤충 에서 진화하였다. 하지만 나비목 곤충이 깡충거미 간의 의사소통 신호를 의태한다는 가설은 제안된 바 없다. 본 연구에서는 깡충거미과의 구애/영역성 행동을 의태하는 것으로 추정되는 붉은꼬마꼭지나방(Atkinsonia ignipicta)의 빗살 모양 더듬이와 추켜 올린 다리가 포식을 단념시키는 의태 신호로 작동하는지 실험적으로 검증 하였다. 깡충거미 의태라 추측되는 붉은꼬마꼭지나방의 형태적 및 행동적 특성들을 단계적으로 제외한 뒤 포식 자(흰눈썹깡충거미, Evarcha albaria)와의 조우 시 생존을 비교하였다. 연구 결과, 붉은꼬마꼭지나방은 비슷한 크기의 비-의태 나방에 비해 포식자의 공격을 덜 받았으며, 더듬이나 다리 중 하나라도 결여되었을 때 흰눈썹깡충 거미의 공격이 증가하였다. 이는 붉은꼬마꼭지나방의 더듬이와 다리 모두가 시각적 방어의 중요한 신호로 작동 한다는 것을 시사한다. 하지만 흰눈썹깡충거미가 붉은꼬마꼭지나방을 향해 구애/영역성 행동을 보이지 않았다 는 점에서 깡충거미의 낮은 공격 빈도가 같은 깡충거미 종류로 오인해서인지 다른 이유에서인지는 불투명하다. 그러나 사층깡충거미(Marpissa pulla)는 붉은꼬마꼭지나방을 상대로 영역성 행동을 잦은 빈도로 보였으며, 이는 붉은꼬마꼭지나방의 형태가 깡충거미 의태 효과를 가진다는 것을 보여준다.