Do these large spiders in Taiwan belong to different species?
The following is from Biogeography and Speciation Patterns of the Golden Orb Spider Genus Nephila (Araneae: Nephilidae) in Asia, Yong-Chao Su, Yung-Hau Chang, Deborah Smith, Ming-Sheng Zhu, Matjaž Kuntner and I-Min Tso, Zoological Science, 28(1):47-55. 2011., DOI: 10.2108/zsj.28.47 http://www.bioone.org/doi/full/10.2108/zsj.28.47

Spider 1 seems a good match for C in the images below, and Spider 2 matches A and B. So I propose that both spiders are Nephila pilipes but with different color patterns. 






  Fig. 1. Nephila diversity in Asia and Australia and its extreme sexual size dimorphism: (A–E), N. pilipes; (A–B), female of the common color pattern, Taiwan; (C–D), female of the darker color pattern, Taiwan; (E), male (arrow) in copulatory pose on female, Singapore; (F–G), female N. antipodiana, Singapore; (H), female N. plumipes, Australia; (I–J), female N. clavata, Taiwan. Images by M. Kuntner (www.nephilidae.com).